Conduct screen reader/keyboard testing

[thatbudakguy]

We don't have to go super deep on this, but making an effort before asking for SODA review is a good idea.

Using safari with VoiceOver active, tab/keyboard navigate through and check the rotor/headings/links panels for:

• homepage
• search index page (+ perform a search)
• show page (activating downloads, using the viewer, etc.)

Issues identified with the viewer can be considered out of scope (but obviously will need to addressed) because they might need to be handled in sul-embed, geoblacklight, mirador, etc...