Add a script to cycle through language switching modes.

[CyrilleB79]

Link to issue number:

Fixes #10253

Summary of the issue:

A gesture is missing to control automatic language switching and automatic dialect switching options.

Description of how this pull request fixes the issue:

Add an unassigned script that cycles through the 3 following automatic language and dialect switching modes:

• Language and dialect switching off
• Language switching on, dialect switching off
  • Language and dialect switching on

Note that the 4th possible state (language switching off and dialect switching on) does not make sense.

Testing strategy:

• Called the script many times and checked the result in the Speech Settings panel after each call
• Tested with eSpeak in French (Franche) the text on this test page: ExamplePageWithLangTag.html.txt
  Note: The number 70 is said to be "soixante-dix" in French from France and "septante" in French from Belgium. Hence the easy test to distinguish one dialect from another.

Known issues with pull request:

In #10253, the alternative solution to include this toggle in the synth setting ring was suggested by @JulienCochuyt.
Since the synth settings ring already contains many parameters, I have not retained this solution. Should #7747 be implemented, we can re-discuss it at that time.
Also a dedicated gesture is faster than the ring and thus would fulfill the expectations of #10253 (comment).

Change log entries:

New features
An unassigned script to cycle through language and dialect switching modes have been added. (#10253)

Code Review Checklist:

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

[AppVeyorBot]

• PASS: Translation comments check.
• PASS: Unit tests.
• FAIL: Lint check. See test results for more information.
• PASS: System tests.
• Build (for testing PR): https://ci.appveyor.com/api/buildjobs/1v3yqbto295lt8im/artifacts/output/nvda_snapshot_pr13680-25376,b455bd0f.exe

See test results for failed build of commit b455bd0f30

[seanbudd]

Thanks @CyrilleB79 - LGTM otherwise