Ace spell checker

[mkslanc]

Issue #, if available: #2107

Description of changes:

• Provide example for integration of new Ace SpellCheck , which provides syntax-aware spell-check diagnostics for text
  * works with conjunction with ace-linters
• fixes small bug with not rendered correct option state after reload
  By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

To test:

1. Simply turn on new Use Spell Checker option on options panel

Pull Request Checklist:

• No backwards incompatible changes were made to Ace's public interface which is defined through the main typings file (ace.d.ts) and its references:
  • https://github.com/ajaxorg/ace/blob/master/ace.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-modes.d.ts
  • https://github.com/ajaxorg/ace/blob/master/ace-extensions.d.ts

Open kitchen-sink @ 3eddc9d515cbaf85ebb52b9d815505d2c910aa36

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.78%. Comparing base (05fbd6a) to head (3eddc9d).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5923   +/-   ##
=======================================
  Coverage   87.78%   87.78%           
=======================================
  Files         623      623           
  Lines       45931    45931           
  Branches     7646     7646           
=======================================
  Hits        40322    40322           
  Misses       5609     5609           

Flag	Coverage Δ
unittests	87.78% <ø> (ø)

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