Implement prophet-bounded-context crate #2

Create the prophet-bounded-context crate for keeping track of the entity ReSSAs from the prophet-ressa-run crate (will be renamed from prophet-ressa-minify. The output context of the ReSSA will be used to create a more structured form of the context of the detected entities.

For this, we need the contexts returned by the ReSSAs to have a consistent format so they can be converted.