Add grow to xy-cell-base

[flatline-studios]

Add the ability to use the xy-cell-base mixin to grow the flex item to take up all available space.

This is effectively the same as: .flex-child-grow, found @ https://foundation.zurb.com/sites/docs/flexbox-utilities.html#vanilla-flexbox-helper-classes - But there isn't a way to do this through the current SASS mixins.

[kball]

This seems reasonable to me. @brettsmason any objections?

[brettsmason]

@kball No problem with it, though isn't grow the same as our auto behaviour?
In hindsight I probably would of called it grow rather than auto but oh well 😄

[flatline-studios]

@brettsmason Unfortunately not...

AUTO:
flex: 1 1 0px;
GROW (proposed):
flex: 1 0 auto;

Because auto has the flex-basis set to 0px, as well as being told it can shrink, then it won't grow, it will just fit in to whatever is left over.

grow would mean, "Take up AT LEAST your minimum space, and ALWAYS take up some amount of the remaining space (depending on other flex-grow: n elements), but NEVER take up less".

It's basically more aggressive than the flex: 1 1 0px that's set up for auto currently, which fits in with what I'd expect auto to do a lot more, so I think the name auto is perfectly suited.

[brettsmason]

@flatline-studios Thanks for confirming and apologies for my slight lack of understanding there 😄
Sounds a decent idea to me in that case.