Include processing4-javafx in Gradle packaging

[micycle1]

@Stefterv

I think you should consider bundling processing4-javafx with the processing core gradle artifact (as I do in https://github.com/micycle1/processing-core-4/)

Otherwise one cannot use the FX2D renderer.

Also, why must I as a user declare the https://jogamp.org/ repository for jogl? Shouldn't this artifact's gradle do that?