Add text-to-speech gallery

[baskrahmer]

What does this PR do?

Fixes #<issue_number>

Before submitting

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

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📚 Documentation preview 📚: https://torchmetrics--2801.org.readthedocs.build/en/2801/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69%. Comparing base (5b0e9b8) to head (0d59ec8).

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #2801    +/-   ##
=======================================
- Coverage      69%     69%    -0%     
=======================================
  Files         346     332    -14     
  Lines       19146   18970   -176     
=======================================
- Hits        13233   13058   -175     
+ Misses       5913    5912     -1