feat(cli): support custom filename cases

[gregberge]

Closes #118

[codecov]

Codecov Report

Merging #136 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #136   +/-   ##
=======================================
  Coverage   88.75%   88.75%           
=======================================
  Files          25       25           
  Lines         418      418           
  Branches      107      118   +11     
=======================================
  Hits          371      371           
  Misses         35       35           
  Partials       12       12

Impacted Files	Coverage Δ
packages/core/src/h2x/replaceAttrValues.js	72.72% <0%> (ø)	⬆️
packages/core/src/plugins/h2x.js	96.29% <0%> (ø)	⬆️

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