Support `MouseEvent.relatedTarget`

[radqut]

Reproduction example

https://codesandbox.io/p/sandbox/old-butterfly-239l2c?file=%2Fsrc%2FApp.test.js%3A4%2C37

Prerequisites

1. Render the structure below

<div>
      <p data-testid="text1" onMouseLeave={onMouseLeave}>text1</p>
      <p data-testid="text2">text2</p>
</div>

2. Find these fields

  const text1 = screen.getByTestId('text1')
  const text2 = screen.getByTestId('text2')

2. Move the cursor

await user.pointer([{target: text1}, {target: text2}])

Expected behavior

event.relatedTarget should be <p data-testid="text2">text2</p>

Actual behavior

event.relatedTarget is global

User-event version

14.5.1

Environment

Testing Library framework: @testing-library/[email protected]

JS framework: [email protected]

Test environment: [email protected]

DOM implementation: [email protected]

Additional context

No response