Support for mixins

[TheJaredWilcurt]

Mixins are not merged by default, we need to look for them and merge them ourselves.

{
  name: 'MyComponent',
  props: {
    amount: {...}
  },
  mixins: [
    {
      props: {
        color: {...}
      }
    },
    {
      props: {
        amount: {...}
      }
    }
  ]
}