Document config change for release 2.0.0

[remkop]

I could not find the gradle plugin for 2.0.0 in plugins.gradle.org

I looked here:
https://plugins.gradle.org/m2/gradle/plugin/org/beryx/badass-jar/
...and only saw up to release 1.2.0.

Took me a while to figure out that not just the version number but also the name changed
from gradle.plugin.org.beryx:badass-jar:1.2.0 to org.beryx:badass-jar:2.0.0.

That may be good to mention in the README somewhere. :-)