Must be compatible with JDK11

[denis111]

Official Jenkins docker images are based on JDK11 so it's impossible to use this plugin:

Some plugins could not be loaded due to unsatisfied dependencies. Fix these issues and restart Jenkins to re-enable these plugins.

Dependency errors:

Outbound WebHook for build events (0.3.0)
Java (14) or higher required

[karololszacki]

This is a duplicate of #12