Add `TupleTypeReference` interface to the API

[mrazauskas]

Acknowledgement

• I acknowledge that issues using this template may be closed without further explanation at the maintainer's discretion.

Comment

Consider adding TupleTypeReference interface to the API. It is available in Strada and particularly useful in combination with Checker#isTupleType():

function handleTuple(type: ts.TupleTypeReference) {
	// ...
}

if (checker.isTupleType(type)) {
	handleTuple(type as ts.TupleTypeReference);
}