Modify README as part of build process rather than using `SETUPTOOLS_SCM_PRETEND_VERSION`

[paddyroddy]

Is Your Feature Request Related to a Problem? Please Describe

On Slack, from @ntessore:

Interesting, but I feel like we are just moving the "hack" to a different place. I was thinking along the lines of https://github.com/hynek/hatch-fancy-pypi-readme where the README modification is part of the build process itself. But that should really wait until we are at the "encore" stage of the project.

Describe the Solution You'd Like

No response

Describe Alternatives You've Considered

No response

Additional Context

No response

[paddyroddy]

Actually, I don't think this would work @ntessore. We won't have access to git tag --describe in there.

[Saransh-cpp]

I feel that the solution implemented in the CI right now looks good enough. I have never switched documentation link to a specific tag for PyPI, so I don't have any other suggestions for this workflow.