Export component interfaces for `ISelectSingle` and `ISelectMulti`, so other projects can know available properties and $refs

We should only expose *the bare minimum* in the public types that are exported.

so in our repo here, we might do something like

```ts
export interface ISelectMulti {
 onlyTheMostImportantPublicProps: string
}

interface IPrivateSelectMulti extends ISelectMulti {
 otherPropsThatProjectsShouldntNeedToKnowAbout: string
}
```