docs: update README

[FreezyLemon]

Lots of fluff (no need to talk about the struct fields of Frame or enum variants of ChromaSubsampling, just look at the docs!), some outdated or wrong information.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.40%. Comparing base (b8f193c) to head (97a0197).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #78   +/-   ##
=======================================
  Coverage   99.40%   99.40%           
=======================================
  Files           7        7           
  Lines         675      675           
=======================================
  Hits          671      671           
  Misses          4        4           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.