docs: inject version selector to HTML docs

[Borda]

What does this PR do?

automating releases with Lightning-AI/utilities#349

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

PR review

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📚 Documentation preview 📚: https://torchmetrics--2886.org.readthedocs.build/en/2886/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69%. Comparing base (714494b) to head (7613da0).
Report is 1 commits behind head on master.

Additional details and impacted files

@@          Coverage Diff           @@
##           master   #2886   +/-   ##
======================================
  Coverage      69%     69%           
======================================
  Files         346     346           
  Lines       19142   19142           
======================================
  Hits        13230   13230           
  Misses       5912    5912