Marker accessibility

How is marker accessibility achieved in MapBox?

- [ ] Should [default markers](https://docs.mapbox.com/mapbox-gl-js/example/add-a-marker/) be focusable?
- In Google Maps _only_ [_interactive markers are focusable_ and have `role="button"`](https://mapsplatform.google.com/resources/blog/improved-accessibility-maps-javascript-api/):

> Markers now default to the [“img” accessibility role](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/Role_Img), or the [“button” accessibility role](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA/Roles/button_role) if they are interactive (such as when a click event listener is registered). Interactive markers are also keyboard navigable [...]
- (This may also be the case for Leaflet in the future: https://github.com/Leaflet/Leaflet/issues/8116)
- Related: https://github.com/mapbox/mapbox-gl-js/pull/11064/commits/53f0eaf1626938a96d622cea2c12557f43468a42
- [ ] Is there a need for authoring guidance? Similar to Leaflet's [Guideline for accessible markers](https://leafletjs.com/examples/accessibility/#markers-must-be-labelled).
- [ ] [Autopan markers into view on focus](https://github.com/Leaflet/Leaflet/issues/8040) is great for keyboard users, please consider it.

Start with the default markers example and the related Mapbox GL JS pull request commit mentioned in the issue. Compare the listed focus, role, keyboard navigation, authoring guidance, and focus autopanning questions with the current behavior. Done requires a decided accessibility scope and corresponding implementation or guidance, but no target files or tests are identified.

Written by the indexing model from the issue text.