Sync WCAG-2.1 branch contents with its change log and errata

[kfranqueiro]

Reminder: when the time comes to merge, we might want to consider a rebase merge for this rather than a squash merge, to retain the cherry-picking breadcrumb trail.

Background

The 2024-12-12 republication of WCAG 2.1 added a new set of entries to the change log; however, most of these changes were never backported to the WCAG-2.1 branch, and therefore did not make it into the republication. In addition, there were several other errata intended to be common between 2.1 and 2.2 which were neither backported nor referenced in the new change log.

Changes

This branch includes a few sets of changes as a starting point for review and discussion; here's a breakdown. It may be easier to review these on a commit-by-commit basis rather than attempting to view the full diff at once.

• The first commit reverts a change (Replicating the 2.2 errata #3742) that was incorrectly backported from main (applied against pointer-input rather than single-pointer)
• The subsequent commits up until "Sync ED with publication" backport changes that were referenced in the new change log entries but had not been applied to WCAG 2.1
  • Note: I intentionally excluded Change markers: add New visual style and remove unnecessary "text semantics" #1481 and Change "NEW" marker to use W3C blue background #4145, because these were only ever raised as errata against 2.2, not 2.1; these are trivial to backport if we want to
• The "Sync ED with production" commit ports corrections which were applied in TR space but didn't make it into the editor's draft on this branch
• The commits thereafter backport additional changes that were raised as errata common between 2.2 and 2.1 but were not referenced in the 2024-12-12 change log update for 2.1
  • Note: I have initially excluded Update input-purposes for syntax highlighting #3380; this is not mentioned even in 2.2's change log update, and upon scrutiny, I am unsure the change makes sense - these classes are typically used within informative docs, and have no meaning under guidelines. I can backport this for consistency if we would like, in which case Update references to HTML autofill/autocomplete #2486 should likely come with it
• The final commit attempts to further update the change log in anticipation of another republish (I expect there may be heavy commentary on this point)
  • Note I fixed some indentation while I was at it; it will be easier to view ignoring whitespace (add ?w=1 to the commit's URL or choose "Hide whitespace" from the cog menu in the sidebar)

All backports were performed with git cherry-pick -x to include information on the originating commit.

Preview