[libcamera-devel] Documentation: Update more detail developer guide on official site

[Kwang Son]

Currently I search document from official site[1] and
it's less detail compared to own build sphinx document.
I think it will be great official documentation has sidebar, so official
site doc has more detail developer documentation.

For now only show docs.rst
My idea is that make docs.rst to root of docs and has sub-child
docs - original docs content
     - Application Guide
     - Internal Dev Guide - Pipe, IPA, ...

This bring benefit that newbie like me easy to search dev information
without build document.
My concern is that official site use different css or javascript.
So I want to confirm that if I modified sphinx doc and it can be
transited to official site easily by administrator.

[1] https://www.libcamera.org/docs.html