Add NETBEANS-3296 link about Javadoc and Sources

[jgneff]

Add a link to the NetBeans bug report NETBEANS-3296, "Attaching JavaFX
Javadoc and Sources." This commit can help make people aware of issues
such as #44 and some possible ways to work around them.

[abhinayagarwal]

Hi @jgneff ,

Can you move the text inside <div class="alert alert-warning">text</div> ?

[jgneff]

Thanks, @abhinayagarwal. Please let me know if you would like any other changes, and also if you want me to squash my two commits into just one.

[abhinayagarwal]

I missed merging this PR :)

@jgneff does this still hold good? I can see that the Netbeans issue is still unresolved.

[jgneff]

Thanks, Abhinay. Yes, I think the note is still relevant and helpful. There has been some progress. The following two sub-tasks of the bug report are fixed:

• NETBEANS-1396 - Maven: Downloaded javadoc / sources not attached to artifact with classifier
• NETBEANS-3303 - Modular Gradle project fails to recognize Javadoc and Sources

I think the other six sub-tasks of the bug report still occur. For example, I still have to use the work-around to get the Javadoc and Sources recognized in a project using Apache Ant.