Assess new WCAG 2.2 criteria and implement new accessibility checks if there are any gaps

[edhamiltonHO]

• [x] Review changes in WCAG 2.2
• [x] Ensure no focus items get hidden
• [ ] If any gaps raise new tickets to resolve
• [x] Make sure any accessibility checks or scripts are updated to reference 2.2 if necessary

[jeff-horton-ho-sas]

See https://github.com/UKHomeOffice/engineering-guidance-and-standards/pull/361