formatBreakpointMods not applying 2xl, 3xl, or 4xl modifiers

[redallen]

For our components that use breakpoint modifers, breakpointMods={[{modifier: "mod-3xl"}]} is not working because the - is not being converted into an _. We should fix the formatBreakpointMods to accommodate /mod-\dxl/.

[redallen]

Fixed in #4270

[redallen]

#4270 only fixed 2xl, not 3xl or 4xl. Reopening