Update accessibility to WCAG 2.2

[jeff-horton-ho-sas]

Is this pull request a content or a code change? (Please fill in the relevant section and delete the other)

Code change

I can confirm:

Accessibility considerations

• [X] This change might impact accessibility and is not covered by automated aXe tests - manual testing has been performed

Review of site and accessibility guidance to bring it up to compliance with WCAG 2.2.

WCAG2.2 changes: https://www.w3.org/WAI/standards-guidelines/wcag/new-in-22/

• [X] 2.4.11 Focus Not Obscured (Minimum) (AA)
  • We don't have banners/modals/other elements that appear over the page content
  • Updated layout accessibility guidance to indicate this assumption
• [X] 2.5.7 Dragging Movements (AA)
  • The site is not interactive in this way - covered by existing assumption statements
• [x] 2.5.8 Target Size (Minimum) (AA)
  • axe-core has an automated check for this, which has been explicitly enabled as it's off by default at the moment.
  • The breadcrumbs are failing this on /standards/managing-secrets/, /standards/signing-code-commits/, and /patterns/using-generative-ai/ - which looks to be an axe bug as they display the same as other pages that pass, and adding space doesn't help. Resolved, forced breadcrumbs to minimum 24px tall.
• [x] 3.2.6 Consistent Help (A)
  • There is a feedback link in the phase banner which is in the same place on all pages ✅
  • There is accessibility link in the footer that is consistent across all pages ✅
  • Question: do we want a more explicit get help link in the footer?
• [X] 3.3.7 Redundant Entry (A)
  • The site doesn't provide forms for users to submit
  • Updated layout accessibility guidance to indicate this assumption
• [X] 3.3.8 Accessible Authentication (Minimum) (AA)
  • The site does not have any authentication
  • Updated layout accessibility guidance to indicate this assumption

[jeff-horton-ho-sas]

Discussed 3.2.6 with @edhamiltonHO and @keithkennedyHO. As we're compliant this is ready to merge and an issue will be raised to see if we want to add a help using this site link.