Maintain track size when changing unit

[patak-dev]

When you change a unit, the size is updated to 1fr, 300px, 10%, 4em. We should try to compute a new value for the track size that gives the same approximate size, but with the new unit. It doesn't need to be exact.

[abeledovictor]

Can we use Polished for this enhancement? For em and rem at least, and for percentages maybe we can do the calc getting the container width.

[patak-dev]

Interesting @abeledovictor, that is an option. We could also check how that utility is implemented, maybe it is a one liner that we can include in our utils and avoid the dependency