Add gestures for braille autoScroll commands

[nvdaes]

Link to issue number:

Fixes #20473

Summary of the issue:

Braille autoScroll scripts don't have associated gestures by default.

Description of user facing changes:

Now, gestures for autoScroll braille commands are available by default:

• NVDA+alt+k: toggles autoScroll.
• NVDA+alt+j: Decreases scroll rate.
• NVDA+alt+l: Increases scroll rate.

Description of developer facing changes:

None.

Description of development approach:

N/A.

Testing strategy:

Tested locally.

Known issues with pull request:

None.

Code Review Checklist:

• Documentation:
  • Change log entry
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English
• API is compatible with existing add-ons.
• Security precautions taken.

[nvdaes]

@Qchristensen and others, I've created this PR. Perhaps we should wait to complete this after #20477 is merged?
Please let me know if anything else is needed.