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

[Johan Vos]

On Fri, 4 Sep 2020 11:51:59 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> Looks fine. Did you want to add a note about the additional Javascript bridge restrictions, similar to [this
> note](https://github.com/openjdk/jfx/blob/331a39be016a284e5495c73726e7b58e7769a75e/doc-files/release-notes-14.0.1.md#list-of-security-fixes)
> that was done for 14.0.1? Either way is fine with me.

My first thinking was *not* to add the note here as well, since it is in 14.0.1 and there are no fixes in 14.0.1 that
are not in 15-GA, hence 15-GA implicitly assumes all release notes and docs from 14.0.1.

But on the other hand, since we list the fix in the 15 release notes, it makes sense to add the restriction list here
too. I'll add it..

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