Add HTMLRewriter class in Python SDK

[ryanking13]

This adds HTMLRewriter class in Python SDK, which does proxy lifetime handling internally.

We have an example that uses HTMLRewriter, but it uses JS API directly which is slightly annoying to use in Python because of the proxy handling.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.35%. Comparing base (d2c9058) to head (7bfded9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5945      +/-   ##
==========================================
- Coverage   70.35%   70.35%   -0.01%     
==========================================
  Files         408      408              
  Lines      108651   108651              
  Branches    17991    17991              
==========================================
- Hits        76444    76441       -3     
- Misses      21409    21410       +1     
- Partials    10798    10800       +2     

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[codspeed-hq]

Merging this PR will not alter performance

✅ 70 untouched benchmarks
⏩ 129 skipped benchmarks¹

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_{Comparing gyeongjae/htmlrewriter-2 (7bfded9) with main (d2c9058)}

Footnotes

1. 129 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩