[jfx15] RFR: 8252784: Create release notes for JavaFX 15

[Johan Vos]

Fix for JDK-8252784

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Commit messages:
 - add links
 - Add release notes for JavaFX 15

Changes: https://git.openjdk.java.net/jfx/pull/296/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx&pr=296&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8252784
  Stats: 125 lines in 1 file changed: 125 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/296.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/296/head:pull/296

PR: https://git.openjdk.java.net/jfx/pull/296