Add a mention of the PR review process and proposals to the contribution guide (#4801)

Co-authored-by: Hugo Locurcio <[email protected]>

community/contributing/ways_to_contribute.rst

@@ -84,7 +84,8 @@ To ensure good collaboration and overall quality, the Godot developers
 enforce some rules for code contributions, for example regarding the style to
 use in the C++ code (indentation, brackets, etc.) or the Git and PR workflow.
 
-A good place to start is by searching for issues tagged as `junior jobs <https://github.com/godotengine/godot/issues?q=is%3Aissue+is%3Aopen+label%3A%22junior+job%22>`_ (or `Hacktoberfest <https://github.com/godotengine/godot/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+label%3AHacktoberfest+>`_ during October) on GitHub.
+A good place to start is by searching for issues tagged as `junior jobs <https://github.com/godotengine/godot/issues?q=is%3Aissue+is%3Aopen+label%3A%22junior+job%22>`_
+(or `Hacktoberfest <https://github.com/godotengine/godot/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aopen+label%3AHacktoberfest+>`_ during October) on GitHub.
 
 .. seealso:: Technical details about the PR workflow are outlined in a
              specific section, :ref:`doc_pr_workflow`.
@@ -93,6 +94,22 @@ A good place to start is by searching for issues tagged as `junior jobs <https:/
              tool used to enforce them are outlined in
              :ref:`doc_code_style_guidelines`.
 
+All pull requests must go through a review process before being accepted.
+Depending on the scope of the changes, it may take some time for a maintainer
+responsible for the modified part of the engine to provide their review.
+We value all of our contributors and ask them to be patient in the meantime,
+as it is expected that in an open source project like Godot, there is going to be
+way more contributions than people validating them.
+
+To make sure that your time and efforts aren't wasted, it is recommended to vet the idea
+first before implementing it and putting it for a review as a PR. To that end, Godot
+has a `proposal system <https://github.com/godotengine/godot-proposals>`_. Its
+usage is encouraged to plan changes and discuss them with the community. Implementation
+details can also be discussed with other contributors on the `Godot Contributors Chat <https://chat.godotengine.org/>`_.
+
+.. note:: Proposals are only required when working on an enhancement or a new feature.
+          Bug reports are sufficient for fixing issues.
+
 Testing and reporting issues
 ----------------------------