[Maybe] Dependency Analysis – support severity=warn

[jjohannes]

If this plugin is combined with the dependency-analysis-gradle-plugin (DAGP) it registers a post processing task to report found issues mapped to the module-info.java notation.

You can deactivate failing on certain issues by setting them to severity("ignore"). This works because the issues are then filtered out by the DAGP itself.

You can also set severity("warn"), but this has no effect here. Is is because we do not consider the severity in our post processor.

Documentation:
https://github.com/autonomousapps/dependency-analysis-gradle-plugin/wiki/Customizing-plugin-behavior#failure-conditions-and-filtering