Add configuration option to define which dependency scopes to include in the check

I would like to exclude test dependencies from the banDuplicateClasses check, I'm only interested in what ends up in the WEB-INF/lib classpath of my webapp.

I actually wrote a similar plugin before discovering this one that's already in the central maven repo; I don't want to duplicate efforts but I miss scope configurability. Feel free to take any useful code from https://github.com/mirkonasato/maven-dependency-sanity-plugin