Add partiql mode

[jpschorr]

Add syntax mode for PartiQL (https://partiql.org/)

Note: this PR includes/depends on #4629 (Add ion highlight mode), as PartiQL can embed literal ion values.

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

[codecov]

Codecov Report

Merging #4630 (7fa7e8c) into master (8a991cc) will increase coverage by 0.02%.
The diff coverage is 86.00%.

@@            Coverage Diff             @@
##           master    #4630      +/-   ##
==========================================
+ Coverage   71.09%   71.11%   +0.02%     
==========================================
  Files         547      551       +4     
  Lines       55429    55529     +100     
  Branches    10391    10395       +4     
==========================================
+ Hits        39405    39491      +86     
- Misses      16024    16038      +14     

Flag	Coverage Δ
unittests	71.11% <86.00%> (+0.02%)	⬆️

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Impacted Files	Coverage Δ
lib/ace/mode/ion.js	75.86% <75.86%> (ø)
lib/ace/mode/partiql.js	75.86% <75.86%> (ø)
lib/ace/mode/ion_highlight_rules.js	100.00% <100.00%> (ø)
lib/ace/mode/partiql_highlight_rules.js	100.00% <100.00%> (ø)

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