Add new sbt tasks to check that we have a clean release

A task or tasks that we use when creating releases or release candidates.

validate that have only the main resolver(s) - no local, snapshot or staging resolvers - possibly only allow Resolver. DefaultMavenRepository
validate that no dependencies or transitive dependencies have '-SNAPSHOT' in name
only releases that have milestone versions (suffixed like '-M1') can have dependencies or transitive dependencies have milestone versions

pjfanning / sbt-pekko-build