Allow users to define includes/excludes

[ruromero]

Taking into account the variety of the build/lint/etc. tools it looks impossible to support each file/folder ignorance way, so I agree that adding include/exclude patterns to the extension configuration would be the best choice.

Originally posted by @vrubezhny in #755

In order to avoid noise and undesired notifications, users should be able to define their own includes/excludes patterns in the plugin so that it doesn't scan files that are not meaningful.

Maybe a default excludes behaviour like tests/** or src/test/** can be provided