Improve video doc page

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What

Mostly for updating it about the fact that we have ffmpeg now in the native viewer, but some more general polish and revamp.

This is the last ship-blocker for ffmpeg based h264 decoding, so this

• closes Native video decoder via ffmpeg CLI #7607

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using examples from latest main build: rerun.io/viewer
  • Using full set of examples from nightly build: rerun.io/viewer
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!
• If have noted any breaking changes to the log API in CHANGELOG.md and the migration guide

• PR Build Summary
• Recent benchmark results
• Wasm size tracking

To run all checks from main, comment on the PR with @rerun-bot full-check.

[github-actions]

Deployed docs

Commit	Link
6b70b2d	https://landing-d79293oob-rerun.vercel.app/docs

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rendered
https://landing-27o0skl6o-rerun.vercel.app/docs/reference/video

[Wumpf]

maybe 🚧 doesn't quite cut it. It's not like we're working on it actively (we can't - hevc support is a legal issue for mozilla). But 🟧 is worse

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trying 🔲 instead