Accessibility Updates

[Rene2mt]

Resolve accessibility issues identified during testing.

[aj-stein-gsa]

@wandmagic per discussion today you and I may want to sit together and checking out what template and theme changes are needed to resolve these issues in part or in whole in this repository. I assume you won't have questions, but let us know.

[wandmagic]

they are mostly minor changes to bring it up to compliance so far, but most edits will be to the theme upstream, i'll link the PR to this issue for visibility and we can take a look at them together

[Rene2mt]

Upstream fixes to USWDS theme - GSA/uswds-hugo#267