chore(a11y): add missing role='search' and type='search' in navbar component and examples

[julien-deramond]

@Aniort pointed out to @Nurovek in his WIP development of Global Headers a missing role=search as an attribute of the <form>s.

This PR is a proposal to apply this feedback all over Boosted documentation.

If this PR is merged, @ffoodd , do you think Bootstrap would be interested in such a modification?

[ffoodd]

Maybe, but check first if it's been already tried, to not waste your time 😉

[ffoodd]

Not 100% sure but please try 😄

FWIW pa11y-ci might complain about multiple search roles in the same page.

Maybe a callout to mention the role would help, too?

[julien-deramond]

Not 100% sure but please try 😄

FWIW pa11y-ci might complain about multiple search roles in the same page.

Maybe a callout to mention the role would help, too?

• Run npm run docs-accessibility locally to check pa11y results (because not really still stable in GitHub CI)
• Add a callout to mention the role
• When this PR is merged, propose a PR to Bootstrap. It seems not having being proposed yet so it's worth trying.
  • Add missing role="search" and type="search" in navbar doc and examples twbs/bootstrap#35223

@ffoodd and/or @yannickcornaille, do the location and the content of the callout seem OK to you? (see https://deploy-preview-785--boosted.netlify.app/docs/5.1/components/navbar/#forms)