Ensure that all existing aria- elements are known and allowed

[mozfreddyb]

I'll make a list of all existing aria- attributes. We do not want to remove accessibility features from HTML.

Sidenote: We do not have the same issue with data- attributes. Those attributes are removed by default and can be kept with a configuration as they will not be listed in known attributes. For aria, we want to keep them by default.

[mozfreddyb]

The Mozilla a11y friends tell me that the section 6.7 Definitions of States and Properties (all aria- attributes)* in the ARIA spec does indeed contain all aria attributes 😅. That made it relatively easy and I got them out of the spec in a hacky way using a code snippet like Array.from($("#index_state_prop").querySelectorAll("dt")).map(el => el.textContent) in DevTools.

I'm going to submit a pull request to add them to our known attribute list

aria-activedescendant aria-atomic aria-autocomplete aria-braillelabel aria-brailleroledescription aria-busy aria-checked aria-colcount aria-colindex aria-colindextext aria-colspan aria-controls aria-current aria-describedby aria-description aria-details aria-disabled aria-dropeffect aria-errormessage aria-expanded aria-flowto aria-grabbed aria-haspopup aria-hidden aria-invalid aria-keyshortcuts aria-label aria-labelledby aria-level aria-live aria-modal aria-multiline aria-multiselectable aria-orientation aria-owns aria-placeholder aria-posinset aria-pressed aria-readonly aria-relevant aria-required aria-roledescription aria-rowcount aria-rowindex aria-rowindextext aria-rowspan aria-selected aria-setsize aria-sort aria-valuemax aria-valuemin aria-valuenow aria-valuetext