refactor: implement prop types

[MichaHuhn]

Implement prop types by using the type-based declaration.

Convert the runtime declaration:

defineProps({
  icon: {
    type: Object as () => CustomIcon
  }
})

to the type-based declaration:

defineProps<{
  icon: CustomIcon
}>()

The type-based declaration provides type-safety and autocompletion when using props. The prop types work exactly like the emit types (#199).