Use `rule.selectors`
Wring CSS values

  - 0px => 0
  - 0 0 0 0 => 0
  - 0.6 => .6
  - rgb(51, 102, 153) => #336699
  - hsl(22, 48.245823%, 34.8592227%) => #844d2e
  - #336699 => #369
Version 0.0.3