RFR: 8361713: JavaFX API docs overview is missing an intro section [v2]

[Kevin Rushforth]

> This PR adds an introductory section to the JavaFX API docs similar to that of the JDK docs.
> 
> Compare the [JavaFX 24 API docs](https://download.java.net/java/GA/javafx24/docs/api/index.html) with the [JDK 24 API docs](https://docs.oracle.com/en/java/javase/24/docs/api/index.html).

Kevin Rushforth has updated the pull request incrementally with one additional commit since the last revision:

  add missing </li> tag

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Changes:
  - all: https://git.openjdk.org/jfx/pull/1842/files
  - new: https://git.openjdk.org/jfx/pull/1842/files/392ec6df..4a0e3f3b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jfx&pr=1842&range=01
 - incr: https://webrevs.openjdk.org/?repo=jfx&pr=1842&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1842.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1842/head:pull/1842

PR: https://git.openjdk.org/jfx/pull/1842