Add Quick guide for Doxygen Configurations.

Signed-off-by: Adarsh <Adarshbunny293@gmail.com>

docs/README.md

@@ -152,6 +152,16 @@ XX is a number between 02-99. Currently, 00_revision_history.md
 contains the documentation revision history, and 01_overview.md is the
 overview of the compiler goals and architecture.
 
+## Quick guide for developing the Doxygen documentation
+- Doxygen is configured in `docs/doxygen/doxygen.cfg`.
+- The main HTML page is configured in `docs/doxygen/Doxymain.md`:
+  - CSS for the card effect is in `docs/assets/css/card.css`.
+  - The effect for the Easter egg toggle is defined in `docs/assets/css/flow.css`. 
+  - The homepage P4C architecture is rendered using `docs/assets/architecture_unanimated.html`, with the editable draw file available at `docs/assets/Architecture.drawio`.
+- Add pages and subpages manually to the sidebar (see `docs/doxygen/p4c_layout.xml`).
+- TOCs in markdown files are created with the `[TOC]` command.
+- The base style for Doxygen Awesome is described in the [Doxygen Awesome Documentation](https://jothepro.github.io/doxygen-awesome-css/) and the updated color scheme is defined in [`docs\assets\css\p4c_custom.css`](https://github.com/p4lang/p4c/blob/main/docs/assets/css/p4c_custom.css).
+
 ## Documentation Comments Style Guide 
 - Use triple slashes `///` for documenting functions and classes in files.
 - Double slashes `//` should be used for "internal" comments within functions.