Support for non-greedy/lazy wildcards

Hey,

I've recently found about about this package and started to convert or regexes :)

One major thing I noticed missing is the ability to add lazy/non-greedy wildcards. I thing All functions that make use of the '' or '+' wildcard should have an optional parameter or an equivalent functions that uses '?'/'+?' Since the code puts most of the expressions in a non-capturing group we can't just use .add('?') afterward.

This was discussed a bit in the dart repo. This is really important to avoid unexpected inclusion in the wildcard.

Effected functions: anything, anythingBut, something, somethingBut, multiple.

OneOrMore should probably be included as well but currently it doesn't use a non-capturing so we still follow it up with .add('?')