Update Braille Reading and Automatic Scroll Rate in User Guide (#20477)
Summary of the issue:
Moved from PR #20457 to make change against beta rather than master. Accommodated the suggestions from that PR and also expanded scope to add a new "Braille Reading" topic under the main Braille section which includes a sub-section on automatic Braille scrolling.
Also added tables for Braille reading and input commands. These have many unassigned gestures. The intention is to eventually document all unassigned gestures in their respective sections of the user guide.
Initially prompted because automatic braille scrolling requires an unassigned gesture to be used in order to work. This wasn't 100% obvious in the documentation originally (at least not to me).