Add support for rem values in gap and peek

[krmax44]

This allows the use of relative sizes with rem in peek and gap instead of just pixel units.

[krmax44]

hey @jedrzejchalubek, do you have some time to review/merge this?

[jedrzejchalubek]

I think this logic here can be simplified following way:

export function toPx (value) {
  if (value.endsWith('rem')) {
    const { fontSize } = window.getComputedStyle(document.documentElement)
    return toInt(int * toFloat(fontSize))
  }

  return toInt(value)
}

[jedrzejchalubek]

Other than that looks LGTM :)

[krmax44]

@jedrzejchalubek Sorry for getting back so late! This would unfortunately cause an error whenever value is not a string, though.