Add option to 'reset' grid at breakpoints

[meowsus]

Hey,

While working with the grid I ran into a situation where toggling from a width-based grid to an automatic grid at a breakpoint made sense.

Would you be interested in a PR for this functionality? Or do you think it might open up the floodgates for the use case of switching from an automatic grid to a width-based grid?

Let me know and I'd happily submit the PR to you.

[colourgarden]

I guess a grid 'reset' option where it removes everything width-based may be useful but I'd like to see specific use-cases before committing to introducing this as a feature. Could you provide a use-case or example for this?

[meowsus]

It's been a few months since I opened this issue, so I'll admit that I don't remember my original use case. I mocked up a simple icon-based utility nav use case, which may be a bit contrived, but I think it'll at least start a discussion:

[colourgarden]

I think, currently, this could be solved with a nested grid but I can see the value in a reset of some sorts. The unset keyword may be useful here so I'll leave this as a feature request for the flexbox rewrite.