update regexp used in schema

[albertywu]

Support both dashes and underscores as valid characters for keys for input and matrix steps.

[timriley]

Thanks very much for your contribution here, @albertywu, and apologies for keeping you waiting for so long! We've just made a couple of changes to this PR:

• Adding test cases to exercise the changes to the regular expressions you've updated
• Removing support for dashes in the matrix setup propertyNames regular expression, since this is not fully supported right now; in particular, we don't currently support dashes for interpolating the matrix setup names into nearby strings

We'll go ahead and merge this now, and will shortly get onto handling your other PR. Thanks again! 💚