more options for nx graph --focus

[ctaepper]

Especially for debugging it would be great to add an option here which would limit the shown dependencies of the focused project to either incoming or outgoing dependencies, something like nx graph --focus mylib --direction in.

example use case:
we have user-profile library, which itself depends only on a few utility libraries. but the user-profile lib is imported into many other libs. now I want to use the graph to verify that this lib really only depends on the other libs it should. I was not able to do that - when focusing the user lib I always see both in and outgoing libs which in our case results in many (many) libs. Using the start/stop feature does not really do the same.