feat(expandIconRender): Add expandIconRender prop for overriding expa…

[hrgui]

…ndIcon

Closes #186

will do unit tests once i understand how they are done

[codecov-io]

Codecov Report

Merging #187 into master will decrease coverage by 0.12%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #187      +/-   ##
==========================================
- Coverage   96.06%   95.93%   -0.13%     
==========================================
  Files          17       17              
  Lines         712      714       +2     
  Branches      189      190       +1     
==========================================
+ Hits          684      685       +1     
- Misses         26       27       +1     
  Partials        2        2

Impacted Files	Coverage Δ
src/ExpandableTable.js	98.11% <ø> (ø)	⬆️
src/ExpandableRow.js	95.23% <66.66%> (-2.27%)	⬇️

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[yesmeck]

Yes, please add a test case, and I'd prefer expandIcon as the name.

[yesmeck]

#236