feat: add nasal language

[BobDotCom]

Description of changes:
Adds syntax highlighting for the Nasal scripting language.

Nasal (Not Another Scripting LAnguage) is FlightGear's built-in scripting language.
https://wiki.flightgear.org/Nasal
http://plausible.org/nasal
https://github.com/BobDotCom/Nasal.tmbundle

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[InspiredGuy]

Thank you for the contribution! The build has failed due to one of the regular expressions, could you please take a look? It would also be great if you could add a test for this newly added mode, there are examples of tests in https://github.com/ajaxorg/ace/tree/master/src/mode like https://github.com/ajaxorg/ace/blob/master/src/mode/javascript_test.js

[BobDotCom]

Thank you for the contribution! The build has failed due to one of the regular expressions, could you please take a look? It would also be great if you could add a test for this newly added mode, there are examples of tests in https://github.com/ajaxorg/ace/tree/master/src/mode like https://github.com/ajaxorg/ace/blob/master/src/mode/javascript_test.js

@InspiredGuy The regex should be fixed now. Do the tests need to be added now or can I add them in a later PR?

[InspiredGuy]

@BobDotCom the build now fails due to linter errors, please take a look. We would prefer tests to be added to this PR, but your mode seems to just inherit the TextMode and not add any new behaviours so it should be fine as is. I would only ask to generate tokens for highlight rules test - see https://github.com/ajaxorg/ace/blob/master/src/mode/_test/Readme.md.

[BobDotCom]

@InspiredGuy I fixed those linter errors and generated the tokens, does that look good?

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (7a6b83e) 87.41% compared to head (1d253c1) 87.47%.
Report is 13 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5342      +/-   ##
==========================================
+ Coverage   87.41%   87.47%   +0.06%     
==========================================
  Files         574      579       +5     
  Lines       45613    45877     +264     
  Branches     6935     6954      +19     
==========================================
+ Hits        39873    40133     +260     
- Misses       5740     5744       +4     

Flag	Coverage Δ
unittests	87.47% <100.00%> (+0.06%)	⬆️

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Files	Coverage Δ
src/mode/nasal.js	100.00% <100.00%> (ø)
src/mode/nasal_highlight_rules.js	100.00% <100.00%> (ø)

... and 15 files with indirect coverage changes

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[InspiredGuy]

Looks good @BobDotCom , thank you