feat: Add proposals section, and NGINX App Protect WAF Refactor

This commit adds a new documentation folder to the repository, with a
discrete section for proposals. I will be using this folder in the
future to organise more process documentation.

NGINX App Protect WAF has had a lot of fundamental design problems with
how its documentation is structured due to historic changes in the
direction of the product. Since those changes, the documentation has not
changed to account for it.

Author: ADubhlaoich

documentation/README.md

@@ -0,0 +1,15 @@
+# NGINX Documentation repository 
+
+This directory contains the documentation for the NGINX Documentation repository.
+
+It's used by the DocOps team to record how we configure our tools and instructions for certain precise tasks.
+
+There's also documentation around our ways of working, and ideas of significance wider than the scope of an issue or pull request.
+
+We maintain this information publicly as part of NGINX's commitment to transparency and open source.
+
+If you're interested in contributing to the [NGINX documentation website](https://docs.nginx.com/), check out [CONTRIBUTING.md](/CONTRIBUTING.md).
+
+## Topics
+
+- [Proposals](/documentation/proposals/README.md)