FF92: AVIF - relnote and image updates

[hamishwillee]

This is final part of docs for AVIF support in FF92 - track in #7744
It includes

• release notes,
• a new preference image.avif.compliance_strictness for controlling strictness of the parser. This is in experimental features.
• Updates to the image guide to remove the preference for enabling the feature, and note the level of support provided.
• Minor changes to HTTP accept header doc to cross link to the list of headers (opportunistic)

Think we're all done.

[github-actions]

Preview URLs

• https://pr8005.content.dev.mdn.mozit.cloud/en-US/docs/Mozilla/Firefox/Releases/92
• https://pr8005.content.dev.mdn.mozit.cloud/en-US/docs/Mozilla/Firefox/Experimental_features
• https://pr8005.content.dev.mdn.mozit.cloud/en-US/docs/Web/Media/Formats/Image_types
• https://pr8005.content.dev.mdn.mozit.cloud/en-US/docs/Web/HTTP/Headers/Accept

Flaws

Note! 2 documents with no flaws that don't need to be listed. 🎉

URL: /en-US/docs/Mozilla/Firefox/Releases/92
Title: Firefox 92 for developers
on GitHub
Flaw count: 1

• macros:
  • /en-US/docs/Web/CSS/font-face does not exist

---

URL: /en-US/docs/Mozilla/Firefox/Experimental_features
Title: Experimental features in Firefox
on GitHub
Flaw count: 2

• macros:
  • /en-US/docs/Web/API/Document/autoplayPolicy does not exist
• sectioning:
  • 'Property_math-style' is not a unique ID in this HTML (temporarily changed to Property_math-style_2)

External URLs

URL: /en-US/docs/Mozilla/Firefox/Releases/92
Title: Firefox 92 for developers
on GitHub

• 🚨 http://aomedia.org/ (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Mozilla/Firefox/Experimental_features
Title: Experimental features in Firefox
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/Media/Formats/Image_types
Title: Image file type and format guide
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/HTTP/Headers/Accept
Title: Accept
on GitHub

No new external URLs

[hamishwillee]

@Rumyra Would be great to get a review on this when you have a chance. Worried other PRs will mean I have to start doing complicated merges.