Mention alternative slash official way too

[martinmosegaard]

As we just talked about, another way is to use the built-in [https://docs.gradle.org/current/userguide/application_plugin.html](application plugin). With other pros and cons compared to the uberjar approach.

So it could be changed from becoming-insane to two-ways-to-package-an-executable-groovy-application-with-gradle. Sort of like two of these [https://www.anexinet.com/blog/six-ways-to-package-a-java-application-with-gradle/](six ways).

Maybe I can make a PR at some point.