add highlighting support for Single-Assignment C

[hv15]

Description of changes:

With this PR I'd like to include support to syntax highlight Single-Assignment C code, which is a functional array programming language (see https://sac-home.org for more info) with a very similar syntax to C/C++.

The mode rules are based off of the ace C/C++ mode file, but SaC is a subset of C so I've omitted a lot from it (it didn't make sense to extend it).

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

[hv15]

has anyone had a chance to look at this yet?

[codecov]

Codecov Report

Merging #4625 (354aba6) into master (8a991cc) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4625      +/-   ##
==========================================
+ Coverage   71.09%   71.15%   +0.06%     
==========================================
  Files         547      549       +2     
  Lines       55429    55463      +34     
  Branches    10391    10391              
==========================================
+ Hits        39405    39467      +62     
+ Misses      16024    15996      -28     

Flag	Coverage Δ
unittests	71.15% <100.00%> (+0.06%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
lib/ace/mode/sac.js	100.00% <100.00%> (ø)
lib/ace/mode/sac_highlight_rules.js	100.00% <100.00%> (ø)
lib/ace/editor.js	81.69% <0.00%> (+1.97%)	⬆️

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