Pseudo classes should work on pseudo elements

API should be:

```js
<Ook
  after={{
    content: 'Eek!',
    position: 'absolute',
    top: '100%',
    right: '0px',
    width: '100px',
    height: '100px',
    background: 'green',
    display: 'flex',
    alignItems: 'center',
    justifyContent: 'center',

    hover: {
      background: 'blue',
      width: {
        d: '200px'
      }
    }
  }}
/>
```