Initial Modal Widget work tweaks MSC2790

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

src/Modal.tsx

@@ -38,7 +38,7 @@ export interface IModal<T extends any[]> {
     close(...args: T): void;
 }
 
-interface IHandle<T extends any[]> {
+export interface IHandle<T extends any[]> {
     finished: Promise<T>;
     close(...args: T): void;
 }