feat: PHP bindings

[Stranger6667]

• Defaults to CSSInliner (+ also rename for consistency)
• CI (tests, release)
• Docs + Readme
• inline_many
• Cache support
• namespacing?
• Benchmarks
• Update ext-php-rs to 0.14 when it is ready
• Cleanup tests
• Builder for options

CssInliner::inline($html)
CssInliner::options()

[codspeed-hq]

CodSpeed Performance Report

Merging #499 will not alter performance

_{Comparing dd/php (cf4e121) with master (478c565)}

Summary

✅ 6 untouched benchmarks

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.43%. Comparing base (dcd2835) to head (cf4e121).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #499   +/-   ##
=======================================
  Coverage   88.43%   88.43%           
=======================================
  Files          18       18           
  Lines        1919     1919           
=======================================
  Hits         1697     1697           
  Misses        222      222           

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