RFR: 8316135: Create release notes for JavaFX 21

[Andy Goryachev]

On Tue, 12 Sep 2023 17:14:28 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> Release notes for JavaFX 21, including four important changes, and the list of enhancements and bugs fixed in this release.
> 
> I plan to integrate this on Monday, Sep 18th, and backport it to `jfx21` in time for Tuesday's release of JavaFX 21.

that's quite a few bugs fixed!
looking good 🕶

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Marked as reviewed by angorya (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1239#pullrequestreview-1622798186