fix: allow opt-out of Fixes/Refs metadata

[codebytere]

Closes #470.

Allows for a collaborator to skip Fixes: and Refs: being automatically added to generated commit metadata if --skipRefs is passed.

[codecov]

Codecov Report

Merging #474 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #474   +/-   ##
=======================================
  Coverage   82.58%   82.59%           
=======================================
  Files          34       34           
  Lines        1665     1660    -5     
=======================================
- Hits         1375     1371    -4     
+ Misses        290      289    -1     

Impacted Files	Coverage Δ
lib/metadata_gen.js	100.00% <100.00%> (ø)
lib/ci/ci_type_parser.js	81.35% <0.00%> (-0.47%)	⬇️
lib/pr_checker.js	95.49% <0.00%> (ø)

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[richardlau]

Change looks okay but needs tests.