Add documentation to configuration paramters

[U1F984]

It would be great if there was a way to add documentation to configuration parameters. The documentation could be shown in the config report and in case any parameters are missing.

I've also created an issue in JetBrains/java-annotations#104, so if that is approved this standard annotation could be used to provide IDE support to such documentation.

If there is interest in this feature I'm willing to try to implement it.

[sksamuel]

I think this sounds like a good idea. Would be happy to see a PR.