Draft for better write_video documentation

[N00bcak]

Should address some of the suggestions pointed out in #8509 (and possibly resolve #8569).

NOTE: I was unable to get the documentation to build likely due to some other bug (#8575), apologies.

Instead, I cross-checked with other documentation snippets to minimize chances of error.

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/vision/8576

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 2 New Failures

As of commit f8b4945 with merge base 0534b6e ():

NEW FAILURES - The following jobs have failed:

• Lint / c-source / linux-job (gh)
  RuntimeError: Command docker exec -t b8540b362acae14b84dfccb07559ebb13d533fd031cba9a17b040d13df036618 /exec failed with exit code 1
• Tests / unittests-windows (3.9, windows.g5.4xlarge.nvidia.gpu, cuda, 11.8) / windows-job (gh)
  ##[error]fatal: couldn't find remote ref refs/pull/8576/merge

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[NicolasHug]

Thanks a lot for the PR @N00bcak