Using markdown-style javadoc comments (JEP 467)

[Kevin Rushforth]

Now that JavaFX requires JDK 24 to build, we can use features from JDK 
23 and 24 like markdown javadoc comments from JEP 467 [0], which was 
delivered in JDK 23.

Two outstanding pull requests, PR 1873 [1] and PR 1880 [2], have 
proposed changes that do just that.

As was pointed out in a review comment on PR 1873 [3], we should make a 
deliberate decision to start using them and have some guidelines around 
doing so.

To that end, I would propose that developers can start using markdown 
javadoc comments in new APIs and in APIs that are modified such that 
markdown comments would be helpful.

This is not an invitation to do wholesale changing of existing javadoc 
comments to markdown-style comments for docs that otherwise aren't being 
modified.

Comments are welcome.

-- Kevin

[0] https://openjdk.org/jeps/467
[1] https://github.com/openjdk/jfx/pull/1873
[2] https://github.com/openjdk/jfx/pull/1880
[3] https://github.com/openjdk/jfx/pull/1873#discussion_r2283161713