Update the README to reality.

* Mention some more new features added in the last years.
* Make clear that only FreeBSD, Linux and Windows have official support.
  Everything else is community supported.
* Link to the official addons and yquake2remaster.
* Give some hints to bug reporters and contributors.
* Link to CI builds.
* Avoid relative links so that personal forks link back to the main
  projects. If forks want to link to their own ressources, they can
  edit the file.

README.md

@@ -1,26 +1,86 @@
 # Yamagi Quake II
 
-Yamagi Quake II is an enhanced client for id Software's Quake
-II with focus on offline and coop gameplay. Both the gameplay and the graphics
-are unchanged, but many bugs in the last official release were fixed and some
-nice to have features like widescreen support and a modern OpenGL 3.2 renderer
-were added. Unlike most other Quake II source ports Yamagi Quake II is fully 64-bit
-clean. It works perfectly on modern processors and operating systems. Yamagi
-Quake II runs on nearly all common platforms; including FreeBSD, Linux, NetBSD,
-OpenBSD, Windows and macOS (experimental).
+Yamagi Quake II is an enhanced client for id Software's Quake II with
+focus on offline and coop gameplay. Both the gameplay and the graphics
+are unchanged, but many bugs in the last official release were fixed and
+some nice to have features like widescreen support, reliable support for
+high framerates, a modern sound backend based upon OpenAL, support for
+modern game controllers and a modern OpenGL 3.2 renderer were added.
+Unlike most other Quake II source ports Yamagi Quake II is fully 64-bit
+clean. It works perfectly on modern processors and operating systems.
+
+This code is built upon Icculus Quake II, which itself is based on Quake
+II 3.21. Yamagi Quake II is released under the terms of the GPL version
+2. See LICENSE for further information:
+
+* [LICENSE](https://github.com/yquake2/yquake2/blob/master/LICENSE)
+
+Officially supported operating systems are:
+
+* FreeBSD
+* Linux
+* Windows
+
+Beside theses Yamagi Quake II has community support for MacOS and most
+other unixoid operating systems, including NetBSD, OpenBSD and Solaris.
+
+
+## Addons and partner projects
+
+This repository contains Yamagi Quake II itself. The official addons
+have their own repositories:
+
+* [The Reckoning](https://github.com/yquake2/xatrix)
+* [Ground Zero](https://github.com/yquake2/rogue)
+* [Three Waves Capture The Flag](https://github.com/yquake2/ctf)
+
+Yamagi Quake II Remaster is a project providing optional support for the
+assets of Quake II Remaster by Nightdive Studios and has a less
+conservative approach in regards to new features. It also lives in it's
+own repository:
+
+* [Yamagi Quake II Remaster](https://github.com/yquake2/yquake2remaster)
+
+
+## Development
+
+Yamagi Quake II is a community driven project and lives from community
+involvement. Please report bugs in our issue tracker:
+
+* [Issue Tracker](https://github.com/yquake2/yquake2/issues)
+
+We are always open to code contributions, no matter if they are small
+bugfixes or bigger features. However, Yamagi Quake II is a conservative
+project with big focus on stability and backward compatibility. We don't
+accept breaking changes. When in doubt please open an issue and ask if a
+contribution in welcome before putting too much work into it. Open a
+pull request to submit code:
+
+* [Pull Requests](https://github.com/yquake2/yquake2/pulls)
+
+Also have a look at our contributors guide:
+
+* [Contributors Guide](https://github.com/yquake2/yquake2/blob/master/doc/080_contributing.md).
 
-This code is built upon Icculus Quake II, which itself is based on Quake II
-3.21. Yamagi Quake II is released under the terms of the GPL version 2. See the
-LICENSE file for further information.
 
 ## Documentation
 
-Before asking any question, read through the documentation! The current
-version can be found here: [doc/010_index.md](doc/010_index.md)
+Yamagi Quake II has rather extensive documentation covering all relevant
+areas from installation and configuration to package building. Have a
+look at the documentation index:
+
+* [Documentation Index](https://github.com/yquake2/yquake2/blob/master/doc/010_index.md)
+
 
 ## Releases
 
-The official releases (including Windows binaries) can be found at our
-homepage: https://www.yamagi.org/quake2  
-**Unsupported** preview builds for Windows can be found at
-https://deponie.yamagi.org/quake2/misc/
+Yamagi Quake II releases at an irregular schedule. The official releases
+with source code tarballs and prebuild Windows binaries can be found at
+the homepage:
+
+* [Homepage](https://www.yamagi.org/quake2/)
+
+Our CI builds **unsupported** Linux, MacOS and Windows binaries at every
+commit. The artifacts can be found here:
+
+* [Github Actions](https://github.com/yquake2/yquake2/actions)