Add module supporting munit

[Daenyth]

It would be great if this project supported more test frameworks than just scalatest.

From looking at the code, it seems like the vast majority doesn't need to actually be tied to scalatest, but could live in a core package which only contains the helper method implementations. The individual test integrations could then connect those bits to the appropriate test framework hooks (before/after, fixtures, etc)

I'm aware this is a relatively large change but I think it could be done without breaking compatibility for downstream projects using the library already