Add new errata to both 2.1 and 2.2

[mbgower]

This PR adds four changes to the list of errata for WCAG 2.2 and 2.1 TR documents.

The changes are from: #4256, #4040, #4165, and #2296.

Three of the changes are to notes and examples in the specification, which are non-normative according to the 5.1 Interpreting Normative Requirements.

One of the changes is a normative change, restricted to correcting the alphabetical order for the list of defined terms. As such, it falls under Changes that do not functionally affect interpretation of the document.

Previews: 2.1, 2.2

[netlify]

✅ Deploy Preview for wcag2 ready!

Name	Link
🔨 Latest commit	48b6a73
🔍 Latest deploy log	https://app.netlify.com/projects/wcag2/deploys/6876755c65ca280008b939d1
😎 Deploy Preview	https://deploy-preview-4370--wcag2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[kfranqueiro]

The review period has concluded with positive responses, so the individual errata PRs have been merged to main.

Flagging this to remind us that this is awaiting 2.1 backports in #4470, then I will update the dates and commit references in 21.html, before we merge this.

Branch has been updated after 2.1 backports

[kfranqueiro]

After merging #4470 to WCAG-2.1, I have updated the following on this branch:

• 2.1 dates have been updated to reflect the date the backports were merged
• 2.1 entries have had PR refs replaced with backport commit refs
• 2.2 entry referencing the wrong PR has been corrected
• Phrasings have been updated across both versions for consistency with existing entries:
  • Use present progressive tense
  • Use US English spelling of "harmonize", since I spotted other US English spellings elsewhere in the Errata page
  • Front-load and link to the subject of the change where feasible, which also helps automatic cross-referencing within the Understanding docs (this is sadly not visible in Netlify because it only renders when WCAG_VERSION is explicitly set, which is only true for publishes to w3.org, not GitHub Pages)