* [contributing/documentation/building_the_manual] use tabs and admonitions
---------
Co-authored-by: Max Hilbrunner <mhilbrunner@users.noreply.github.com>
Updated output directory in tutorial for manual sphinx-build operations
on godot-docs. It now matches the output directory used by the make
command for godot-docs.
- Merge Community/Contributing and Engine Development into one top-level section, Contributing.
- Structure it in a way that gives equal priority to various ways to contribute, including documentation.
- Rename several articles to be more comprehensive and in line with the overall state of the documentation.
- Rewrite the guide for class reference contributions.
