ZmtLaunchPlugin.java: javadoc jar is added to distribution

src/main/groovy/de/zmt/gradle/ZmtLaunchPlugin.groovy

@@ -26,6 +26,7 @@ public class ZmtLaunchPlugin implements Plugin<Project> {
                 // project's own library and dependencies     
                 from (project.jar)
                 from (project.sourceJar)
+                from (project.javadocJar)
                 from (project.configurations.runtime)
             }