Initial version of sphinx documentation and...

- remove ubuntu 21.04 from CI (end of life)
- adjust matrix strategy for clang.yml
- Use lessons learned from RetroArcher on localize.yml, crowdin.yml, and locale.py
- Add end of life comments to Dockerfiles
- Adjust dependency order in Dockerfiles

docs/source/building/windows.rst

@@ -0,0 +1,22 @@
+:github_url: https://github.com/SunshineStream/Sunshine/tree/nightly/docs/source/building/windows.rst
+
+Windows
+=======
+
+Requirements
+------------
+First you need to install `MSYS2 <https://www.msys2.org>`_, then startup "MSYS2 MinGW 64-bit" and install the
+following packages using:
+
+.. code-block:: batch
+
+   pacman -S mingw-w64-x86_64-binutils mingw-w64-x86_64-openssl mingw-w64-x86_64-cmake mingw-w64-x86_64-toolchain mingw-w64-x86_64-opus mingw-w64-x86_64-x265 mingw-w64-x86_64-boost git mingw-w64-x86_64-make cmake make gcc
+
+Build
+-----
+.. Caution:: Ensure you are in the build directory created during the clone step earlier before continuing.
+
+   .. code-block:: batch
+
+      cmake -G"Unix Makefiles" ..
+      mingw32-make