Pre-transpile javafx jars into javascript

[johanvos]

Currently, transpiling javafx.graphics.jar (and others) take much time (e.g. 2 minutes). We want to have javafx jars that already contain the transpiled .js files in them. Bck2brwsr has a protocol that allows jars with js in them to be skipped from transpiling, and directly use the .js. In order to do so, a MANIFEST file needs to contain the correct info, see https://github.com/jtulach/bck2brwsr/blob/master/rt/mojo/src/main/java/org/apidesign/bck2brwsr/mojo/AOTLibrary.java