Icon A11y improvements

[StephDriver]

Icons are not being handled accessibly.

Icons are non-text content as per WCAG 1.1.1. The key technique is H86 They must also be semantically identified, as per ARIA24 Technique.

Most of our icons come from Font Awesome, but there are a few others, such as the ORCiD logo, that need individual handling.

For Font Awesome:

• [x] consider implementing Font Awesome's auto accessibility feature
• [ ] if not using auto accessibility then update manually (syntax further down that same page). For each icon:
  • consider whether it is decorative or semantic
  • update icon syntax accordingly.
• [ ] update ORCiD logos to be accessible.
• [x] share icons have already been updated in #3936