Add support for finding buttons that use aria-label for a value.

[bkosborne]

See #779

This adds support for finding a button by its aria-label value.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d8527fd) 98.72% compared to head (98f712c) 98.73%.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #865   +/-   ##
=========================================
  Coverage     98.72%   98.73%           
  Complexity      374      374           
=========================================
  Files            24       24           
  Lines          1022     1024    +2     
=========================================
+ Hits           1009     1011    +2     
  Misses           13       13           

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[maelanleborgne]

As it is very hard to extend the library, I would greatly appreciate if this feature was merged 🙂

[aik099]

As it is very hard to extend the library, I would greatly appreciate if this feature was merged 🙂

@maelanleborgne , can you please be more specific?

P.S.
I've approved this PR.

I've confirmed, that the tests actually test the added code by removing added HTML elements from the test fixtures one by one and witnessing, that tests start to fail after that.

// cc: @stof