Add ARIA Feed role

[geoffrey-eisenbarth]

Implemented keyboard navigation for ARIA's role="feed".

Both MDN and w3.org seem to indicate that a standard for keyboard control is still emerging. They suggest Alt+PgDown to enter a nested feed, but don't mention Alt+PageUp to step outside of the nested feed, which I've implemented.

Please review carefully; I will happily implement any suggestions.

[geoffrey-eisenbarth]

Should I be implementing aria-keyshortcuts for this (and other missing.css ARIA-related JavaScript)?

[dz4k]

Should I be implementing aria-keyshortcuts for this (and other missing.css ARIA-related JavaScript)?

I don't think so, since the key shortcuts are standard