[SDPA-5684] Added a visually hidden list of all validation errors for screenreaders.

[elNico]

Motivation and Context

JIRA issue: https://digital-engagement.atlassian.net/browse/SDPA-5684

Changed

1. Add all submission errors to a visually hidden list.
2. Make sure the list gets read out by screenreaders with priority.
3. Note: This only makes sense in combination with meaningful field validation messages (see screenshots), which are in [SDPA-5526] Added field labels to form validation required messages #1074

Screenshots

Without PR 1074

With PR 1074

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Improvement/refactoring (non-breaking change that doesn't add any features but makes things better)

Checklist

• I've added relevant changes to the documentation.
• I have added tests to cover my changes (if not applicable, please state why)
• My change requires a template update for create-ripple-app.
• I have added template update script for next release.

[dylankelly]

Should this go in the rpl_visually_hidden mixin?

[elNico]

@dylankelly I'm not really sure whether I understand. Can you explain it a bit more? I'm just using the standard rpl_visually_hidden mixin to visually hide the messages. You mean using the rpl-visually-hidden class instead? I wrapped it in the custom _sr-only just because it needed the extra UL treatment. I guess it could be reshuffled if that's what you mean.

[dylankelly]

Yeah maybe i didnt think that through first. What I was probably intending was a list reset mixin that included this.