Add Support for Numeric Separators

[michaelts1]

This PR adds support for numeric separators.

Fixes #3543

[codecov-io]

Codecov Report

Merging #3544 (0d9752e) into master (a8ec9db) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3544   +/-   ##
=======================================
  Coverage   99.78%   99.78%           
=======================================
  Files          52       52           
  Lines        1819     1819           
  Branches      385      385           
=======================================
  Hits         1815     1815           
  Misses          4        4           

Impacted Files	Coverage Δ
src/scanners/javascript.js	100.00% <100.00%> (ø)

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[Rob--W]

Thanks for the patch. LGTM!