Include zanata-editor in the frontend maven module.
it can still have a separate package.json and be in a separate subdirectory (i.e. it can be a separate npm module)
able to build just the npm module that you are working on without having to wait for unrelated parts to build
mvn package should build all the jar files
can be a single jar with all the npm modules under frontend, or separate jars (whichever makes most sense).