Export PhosphorIcon type
Hi, I'd like to ensure a PhosphorIcon is being passed as a prop, but unfortunately this type isn't exported by phosphor-vue.

What I'd like to do is this:
```
const props = defineProps<{
  label: string;
  icon: PhosphorIcon;
}>();
```

And then render with something like this:
```
    <component
      :is="icon"
      :size="20"
      :width="20"
      :weight="isActive ? 'fill' : 'regular'"
    />
```

Would exporting the PhosphorIcon type make sense?
