First stab at file inclusions

[Laurens-W]

What's changed?

Added inclusion as a counter to exclusions

Anything in particular you'd like reviewers to focus on?

Anyone you would like to review specifically?

@sambsnyd

Have you considered any alternatives or workarounds?

Any additional context

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[sambsnyd]

So this is good but does it have exactly the same semantics as the FileInclusion we use in the CLI? If not we're inviting bugs and drift. Can we move that class into rewrite-polyglot and reuse it here, in the maven plugin, and in the Gradle plugin?