[BUG]: Read the Docs, build and prose failed checks in branch `4.x`

[adiati98]

Description

The Read the Docs, build and prose checks are failing in branch 4.x. Below are the error messages:

From Read the Docs app

Sphinx version error:
--
  | The sphinxcontrib.applehelp extension used by this project needs at least Sphinx v5.0; it therefore cannot be built with this version.

Sphinx version we're using in branch 4.x is 4.2.0.

Prose check fails

/home/runner/vale --output=/home/runner/work/_actions/errata-ai/vale-action/reviewdog/lib/rdjsonl.tmpl .
  E100 [lintRST] Runtime error
  
  rst2html not found
  
  Execution stopped with code 1.
Error: Vale and reviewdog exited with status code: 2

The "prose check failed" is happening because Vale can't find rst2html, a program needed to process reStructuredText (.rst) files. But it also might be happening, because there's no step to install Python dependencies, whcih should find and install all dependencies in requirements.txt, as in other branches, as below:

- name: Install Python dependencies
      run: pip3 install -r docs/requirements.txt

Notes

This branch also has no DDEV setup.

Are you willing to help us fix this by making a pull request?

Yes, but I need help

Suggestions (Optional)

• Upgrade the Sphinx version.
• Add a job's step to install Sphinx dependecies in .github/workflows/linting.yml.
• Add DDEV setup.

We can use the setup as we use in other branches (5.2, 6.x and 7.x).

Environment

No response

Screenshots or Screen Recordings (Optional)