Fail fast as an option?

[mrnovalles]

I have been using ex_check in our CI and locally and appreciate the work you've put into the library.

I was wondering if having an option to fail fast, considering the earlier tasks are cheaper than the later ones in the default group.
The scenario would be that running mix check should fail if the formatter is complaining and not run all the tests in ci.

I could look into it myself, pointers to relevant code are appreciated 🙇