Support for helm plugins

It would be good to have an option to execute arbitrary helm plugins.

for this we would need to be able to define plugins in the `pom.xml` similar to this:
```

...

https://github.com/xyz/my-plugin

my-plugin


arg1
arg2

```

No files, tests, or entry points are named. Start by tracing the Maven plugin's existing pom.xml configuration and goal execution path; done means the requested plugin URL, goal, and options can be declared and executed.

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