[A11Y] Adds missing focus rings back to control elements

[davwheat]

Fixes #2656

Changes proposed in this pull request:

This adds back browser default focus outlines to tabbable elements.

Our CSS used to manually remove these outlines for questionable (or no) reasons. These are a critical accessibility feature and must be present.

Reviewers should focus on:

Is there anywhere this does not behave as expected?

Screenshot

Confirmed

• Frontend changes: tested on a local Flarum installation.

[SychO9]

Can we keep it off for FormControls since we already apply styles that match the design on focus ?

I guess there's nothing we can do to only show the outline for these inputs when tabbing 🤔 ?

[davwheat]

Yeah, there's the :focus-visible and :-moz-focusring pseudoclasses. These only show when the browser determines it should show its own focus outline.

Ohh I see what you mean... I'll try some things but I don't think we can...

[SychO9]

Beautiful!