[jfx21u] RFR: Merge jfx:jfx21

[Kevin Rushforth]

Merge `jfx:jfx21` branch into `jfx21u:master` to pick up the release notes.

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Commit messages:
 - Merge jfx:jfx21
 - 8316135: Create release notes for JavaFX 21

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/jfx21u/pull/17/files
  Stats: 153 lines in 1 file changed: 153 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jfx21u/pull/17.diff
  Fetch: git fetch https://git.openjdk.org/jfx21u.git pull/17/head:pull/17

PR: https://git.openjdk.org/jfx21u/pull/17