Removed page summaries from the top of installation and contributing doc pages (#10711)

- Removed page summaries from CONTRIBUTING and installation pages as 
this information was already in the table of contents on the right hand side
- Fixed some broken links in CONTRIBUTING
- Added margin-right tag for when table of contents is being shown
(otherwise the text in the page sometimes overlaps with it)

4 files changed, 21 insertions, 75 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index cd6c34df85..31d0a47fdf 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -2,30 +2,6 @@ Welcome to Synapse
 
 This document aims to get you started with contributing to this repo! 
 
-- [1. Who can contribute to Synapse?](#1-who-can-contribute-to-synapse)
-- [2. What do I need?](#2-what-do-i-need)
-- [3. Get the source.](#3-get-the-source)
-- [4. Install the dependencies](#4-install-the-dependencies)
-  * [Under Unix (macOS, Linux, BSD, ...)](#under-unix-macos-linux-bsd-)
-  * [Under Windows](#under-windows)
-- [5. Get in touch.](#5-get-in-touch)
-- [6. Pick an issue.](#6-pick-an-issue)
-- [7. Turn coffee and documentation into code and documentation!](#7-turn-coffee-and-documentation-into-code-and-documentation)
-- [8. Test, test, test!](#8-test-test-test)
-  * [Run the linters.](#run-the-linters)
-  * [Run the unit tests.](#run-the-unit-tests-twisted-trial)
-  * [Run the integration tests (SyTest).](#run-the-integration-tests-sytest)
-  * [Run the integration tests (Complement).](#run-the-integration-tests-complement)
-- [9. Submit your patch.](#9-submit-your-patch)
-  * [Changelog](#changelog)
-    + [How do I know what to call the changelog file before I create the PR?](#how-do-i-know-what-to-call-the-changelog-file-before-i-create-the-pr)
-    + [Debian changelog](#debian-changelog)
-  * [Sign off](#sign-off)
-- [10. Turn feedback into better code.](#10-turn-feedback-into-better-code)
-- [11. Find a new issue.](#11-find-a-new-issue)
-- [Notes for maintainers on merging PRs etc](#notes-for-maintainers-on-merging-prs-etc)
-- [Conclusion](#conclusion)
-
 # 1. Who can contribute to Synapse?
 
 Everyone is welcome to contribute code to [matrix.org
@@ -35,7 +11,7 @@ follow a simple 'inbound=outbound' model for contributions: the act of
 submitting an 'inbound' contribution means that the contributor agrees to
 license the code under the same terms as the project's overall 'outbound'
 license - in our case, this is almost always Apache Software License v2 (see
-[LICENSE](LICENSE)).
+[LICENSE](https://github.com/matrix-org/synapse/blob/develop/LICENSE)).
 
 # 2. What do I need?
 
@@ -98,17 +74,20 @@ to work on.
 
 # 7. Turn coffee and documentation into code and documentation!
 
-Synapse's code style is documented [here](docs/code_style.md). Please follow
-it, including the conventions for the [sample configuration
-file](docs/code_style.md#configuration-file-format).
+Synapse's code style is documented
+[here](https://matrix-org.github.io/synapse/develop/code_style.html).
+Please follow it, including the conventions for the
+[sample configuration file](https://matrix-org.github.io/synapse/develop/code_style.html#configuration-file-format).
 
-There is a growing amount of documentation located in the [docs](docs)
+There is a growing amount of documentation located in the
+[docs](https://github.com/matrix-org/synapse/tree/develop/docs)
 directory. This documentation is intended primarily for sysadmins running their
-own Synapse instance, as well as developers interacting externally with
-Synapse. [docs/dev](docs/dev) exists primarily to house documentation for
-Synapse developers. [docs/admin_api](docs/admin_api) houses documentation
-regarding Synapse's Admin API, which is used mostly by sysadmins and external
-service developers.
+own Synapse instance, as well as developers interacting externally with Synapse.
+[docs/development](https://github.com/matrix-org/synapse/tree/develop/docs/development)
+exists primarily to house documentation for Synapse developers.
+[docs/admin_api](https://github.com/matrix-org/synapse/tree/develop/docs/admin_api)
+houses documentation regarding Synapse's Admin API, which is used mostly by sysadmins
+and external service developers.
 
 If you add new files added to either of these folders, please use [GitHub-Flavoured
 Markdown](https://guides.github.com/features/mastering-markdown/).
@@ -431,7 +410,7 @@ By now, you know the drill!
 # Notes for maintainers on merging PRs etc
 
 There are some notes for those with commit access to the project on how we
-manage git [here](docs/development/git.md).
+manage git [here](https://matrix-org.github.io/synapse/develop/development/git.html).
 
 # Conclusion
 
diff --git a/changelog.d/10711.doc b/changelog.d/10711.doc
new file mode 100644
index 0000000000..c495f98be8
--- /dev/null
+++ b/changelog.d/10711.doc
@@ -0,0 +1 @@
+Removed table of contents from the top of installation and contributing documentation pages.
\ No newline at end of file
diff --git a/docs/setup/installation.md b/docs/setup/installation.md
index 8540a7b0c1..06f869cd75 100644
--- a/docs/setup/installation.md
+++ b/docs/setup/installation.md
@@ -1,44 +1,5 @@
 # Installation Instructions
 
-There are 3 steps to follow under **Installation Instructions**.
-
-- [Installation Instructions](#installation-instructions)
-  - [Choosing your server name](#choosing-your-server-name)
-  - [Installing Synapse](#installing-synapse)
-    - [Installing from source](#installing-from-source)
-      - [Platform-specific prerequisites](#platform-specific-prerequisites)
-        - [Debian/Ubuntu/Raspbian](#debianubunturaspbian)
-        - [ArchLinux](#archlinux)
-        - [CentOS/Fedora](#centosfedora)
-        - [macOS](#macos)
-        - [OpenSUSE](#opensuse)
-        - [OpenBSD](#openbsd)
-        - [Windows](#windows)
-    - [Prebuilt packages](#prebuilt-packages)
-      - [Docker images and Ansible playbooks](#docker-images-and-ansible-playbooks)
-      - [Debian/Ubuntu](#debianubuntu)
-        - [Matrix.org packages](#matrixorg-packages)
-        - [Downstream Debian packages](#downstream-debian-packages)
-        - [Downstream Ubuntu packages](#downstream-ubuntu-packages)
-      - [Fedora](#fedora)
-      - [OpenSUSE](#opensuse-1)
-      - [SUSE Linux Enterprise Server](#suse-linux-enterprise-server)
-      - [ArchLinux](#archlinux-1)
-      - [Void Linux](#void-linux)
-      - [FreeBSD](#freebsd)
-      - [OpenBSD](#openbsd-1)
-      - [NixOS](#nixos)
-  - [Setting up Synapse](#setting-up-synapse)
-    - [Using PostgreSQL](#using-postgresql)
-    - [TLS certificates](#tls-certificates)
-    - [Client Well-Known URI](#client-well-known-uri)
-    - [Email](#email)
-    - [Registering a user](#registering-a-user)
-    - [Setting up a TURN server](#setting-up-a-turn-server)
-    - [URL previews](#url-previews)
-    - [Troubleshooting Installation](#troubleshooting-installation)
-
-
 ## Choosing your server name
 
 It is important to choose the name for your server before you install Synapse,
diff --git a/docs/website_files/table-of-contents.css b/docs/website_files/table-of-contents.css
index d16bb3b988..1b6f44b66a 100644
--- a/docs/website_files/table-of-contents.css
+++ b/docs/website_files/table-of-contents.css
@@ -1,3 +1,7 @@
+:root {
+    --pagetoc-width: 250px;
+}
+
 @media only screen and (max-width:1439px) {
     .sidetoc {
         display: none;
@@ -8,6 +12,7 @@
     main {
         position: relative;
         margin-left: 100px !important;
+        margin-right: var(--pagetoc-width) !important;
     }
     .sidetoc {
         margin-left: auto;
@@ -18,7 +23,7 @@
     }
     .pagetoc {
         position: fixed;
-        width: 250px;
+        width: var(--pagetoc-width);
         overflow: auto;
         right: 20px;
         height: calc(100% - var(--menu-bar-height));