Fix: Read the Docs, build and prose failed in branch 4.x, and add DDEV configuration

[adiati98]

Description

This PR holds the changes below:

• Updated Sphinx and dependecies versions to follow other existing branches, specifically the default 5.2 branch.
• Add configuration setup to run DDEV for this branch, following other branches.

Important Note

You need to test this out locally and on Codespace to ensure that all changes are working as they should.

Linked issue

Fixes #437

Screenshots or screen recordings

[RCheesley]

I'm not sure if this is fully working, when I spin up a codespace I just get this:

It doesn't seem to be running properly?

[adiati98]

This is weird. I tried build a codespace with this PR and it worked.
Let me take a closer look after I'm back.

[RCheesley]

DDEV works, build-docs works, and Codespaces works too!