Implement a11y in Bookings Page according to latest specs

[davinotdavid]

We recently had an a11y focused inspection in the Bookings Page that generated specifications on how to better implement a11y.

These notes are in Zeplin:

https://zpl.io/LLBoLZJ

[thundernotion]

Issues with a parent cannot be on the Milestones board, removing. Either move your sub-issues up to the parent issue, or turn this into an independent Milestone issue that has sub-issues.