Add custom and accessible outlines

[ben-rogerson]

This PR adds support for the changes to the default outline colors in Tailwindcss@1.9.0:

import tw from 'twin.macro'

tw`outline-none`
tw`outline-black`
tw`outline-white`

// ↓ ↓ ↓ ↓ ↓ ↓

({
  "outline": "2px solid transparent",
  "outlineOffset": "2px"
});
({
  "outline": "2px dotted black",
  "outlineOffset": "2px"
});
({
  "outline": "2px dotted white",
  "outlineOffset": "2px"
});