useBreakpointValue is a custom hook which returns the value for the current
breakpoint from the provided responsive values object. This hook also responds
to the window resizing, returning the appropriate value for the new window size.
size props don't currently accept responsive values
(specified as objects or arrays), but
useBreakpointValue is a good way to
achieve the same behavior.
useBreakpointValue hook returns the value for the current breakpoint.