fix #40: optimize Ruby's regex pattern

[farhan443]

fix #40

Nested quantifier is a common cause of exponential backtracking. In /(do\s*[|](\w+(,\s*\w+)?)+[|])/, there's a nested quantifier 3 levels deep: (\w+(,\s*\w+)?)+.
I replaced it with \w+(,\s*\w+)* so it became 2 levels deep.

The test on https://regex101.com/r/yT5xg0/1/debugger shows that it no longer causes exponential backtracking on string: "do|aaa", but rather linear.

Other change:

• removed the first capture group because it seems to serve no purpose.
• replaced \| with [|] for readability.

[lgtm-com]

This pull request fixes 2 alerts when merging 0073fa1 into 313def7 - view on LGTM.com

fixed alerts:

• 2 for Inefficient regular expression

[codecov]

Codecov Report

Merging #41 (0073fa1) into master (313def7) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #41   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           22        22           
  Lines          824       824           
  Branches        46        46           
=========================================
  Hits           824       824           

Impacted Files	Coverage Δ
src/languages/ruby.ts	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 313def7...0073fa1. Read the comment docs.