RFR: JDK-8312058: Documentation improvements for subscription based listeners [v2]

[Andy Goryachev]

On Mon, 31 Jul 2023 11:51:24 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> Incorporates documentation review comments from #1069.
>> 
>> This PR should be kept minimal so it can be backported to JFX21; it should only contain documentation changes.
>
> John Hendrikx has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Use @implSpec tag
>  - Merge branch 'master' of https://git.openjdk.org/jfx into feature/subscriptions-doc-improvements
>  - Documentation improvements

LvGtm

-------------

Marked as reviewed by angorya (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1177#pullrequestreview-1555368201