Add optional elementRef prop to TransitionComponents

[acelaya]

Part of hypothesis/client#6307

Add a new elementRef prop to TransitionComponents, so that it is possible for consumers to reference their outermost element.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (da09b86) to head (1d8cdaf).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2093   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           71        71           
  Lines         1364      1364           
  Branches       509       509           
=========================================
  Hits          1364      1364           

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