Additional responsive columns for Deck block type

[aileenjeffries]

Currently, the Deck block type allows for setting a different number of columns at various breakpoints. I'm in the process of porting over the Baptist Health case study and think a Deck block for our 5 process graphics would work well. In order to support this, I need two things:
-a max number of columns of at least 5. Might as well make it 6?
-a minimum number of columns of 2. That is, something to replace u-size1of2. As it is now, I can only add columns starting at the "small" breakpoint.