Date-fns to be a peerDep not a dep, bundled with react-day-picker

[Danchev1]

Kind of self-explanatory, but me and my team, we use still version 8, we are building a component library and for calendar we use react-day-picker, the tricky part is that other teams use date-fns separately, so would be a good i think to have it as peerDep only