Fix JSX key attribute clobbering detected value

[comp615]

Why am I submitting this PR

React components have a protected attribute "key" which can seemingly clobber the detected/parsed i18n key due to a naming conflict.

Does it fix an existing ticket?

Yes #1038

Checklist

• [X] only relevant code is changed (make a diff before you submit the PR)
• [X] tests are included and pass: yarn test (see details here)
• [X] documentation is changed or added

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.35%. Comparing base (168c8d5) to head (a95a76b). Report is 57 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1042      +/-   ##
==========================================
- Coverage   95.40%   95.35%   -0.05%     
==========================================
  Files          11       10       -1     
  Lines        1937     1918      -19     
==========================================
- Hits         1848     1829      -19     
  Misses         89       89              

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[karellm]

@comp615 I have mixed feeling about this as some people might be relying on the key attribute. I'd prefer a fix that ignores the key attribute only if the i18nKey one is present. Can you update the PR?