fix: pass the animation event to onAnimationEnd

[pradel]

Closes #522.

Problem

onAnimationEnd was declared and called without arguments, so consumers could not inspect what caused the event.

While investigating I found the handler is attached to the modal dialog and React's animationend bubbles, so any animation ending inside the modal triggered the callback. Worse, while closing, a child animation ending would run setShowPortal(false) and unmount the modal before its own exit animation finished.

Fix

• Pass the React.AnimationEvent<HTMLDivElement> to onAnimationEnd.
• Ignore events whose target is not the modal element itself, so child animations no longer trigger the callback or unmount the modal early.
• Updated the prop type and the docs props table. Existing () => void handlers remain assignable, so this is not a breaking change.

Tests

Added regression tests covering:

• the animation event is passed to onAnimationEnd
• a child animation does not call onAnimationEnd
• a child animation while closing does not unmount the modal

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.69%. Comparing base (070a1f6) to head (1bb638d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #575      +/-   ##
==========================================
+ Coverage   80.40%   80.69%   +0.29%     
==========================================
  Files           7        7              
  Lines         199      202       +3     
  Branches       73       74       +1     
==========================================
+ Hits          160      163       +3     
  Misses         29       29              
  Partials       10       10              

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