Implement a better way to represent fractional values

Many Tailwind CSS utilities support expressions like `1/2` or `3/4` to represent fractional values. For Slipstream modifiers that support fractional values, Slipstream currently treats any value between 0..<1 as a potential fractional value. So `0.25` will be treated as `1/4`.

This is a bit of a hack, isn't super intuitive, and unfortunately due to compiler limitations does not let the developer use the more natural `1/4` to represent the fraction.

A better solution is not immediately apparent, so I'm filing this issue to track the desire for an improvement here.