docs(README): document babelrc option

[jedwards1211]

Please Read the CONTRIBUTING Guidelines
In particular the portion on Commit Message Formatting

The portion on Commit Message Formatting is gone...

Please check if the PR fulfills these requirements

• [NA] Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe: documentation

Does this PR introduce a breaking change?

• Yes
• No

If this PR contains a breaking change, please describe the following...

• Impact:
• Migration path for existing applications:
• Github Issue(s) this is regarding:

Other information:

[codecov]

Codecov Report

Merging #442 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #442   +/-   ##
=======================================
  Coverage   81.08%   81.08%           
=======================================
  Files           6        6           
  Lines         185      185           
  Branches       49       49           
=======================================
  Hits          150      150           
  Misses         18       18           
  Partials       17       17

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[danez]

thanks