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

[jackkoppa]

We should only expose the bare minimum in the public types that are exported.

so in our repo here, we might do something like

export interface ISelectMulti {
 onlyTheMostImportantPublicProps: string
}

interface IPrivateSelectMulti extends ISelectMulti {
 otherPropsThatProjectsShouldntNeedToKnowAbout: string
}