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/macos.rst

@@ -0,0 +1,41 @@
+:github_url: https://github.com/SunshineStream/Sunshine/tree/nightly/docs/source/building/macos.rst
+
+MacOS
+=====
+
+Requirements
+------------
+MacOS Big Sur and Xcode 12.5+
+
+Use either `MacPorts <https://www.macports.org>`_ or `Homebrew <https://brew.sh>`_
+
+MacPorts
+""""""""
+Install Requirements
+   .. code-block:: bash
+
+      sudo port install cmake boost libopus ffmpeg
+
+Homebrew
+""""""""
+Install Requirements
+   .. code-block:: bash
+
+      brew install boost cmake ffmpeg libopusenc
+      # if there are issues with an SSL header that is not found:
+      cd /usr/local/include
+      ln -s ../opt/openssl/include/openssl .
+
+Build
+-----
+.. Caution:: Ensure you are in the build directory created during the clone step earlier before continuing.
+
+   .. code-block:: bash
+
+      cmake ..
+      make -j ${nproc}
+
+If cmake fails complaining to find Boost, try to set the path explicitly.
+
+  ``cmake -DBOOST_ROOT=[boost path] ..``, e.g., ``cmake -DBOOST_ROOT=/opt/local/libexec/boost/1.76 ..``
+