Define a set of interfaces for the ETA repository

src/repositories/shuttle/eta/SelfUpdatingETARepository.ts

@@ -0,0 +1,9 @@
+import { ETAGetterRepository } from "./ETAGetterRepository";
+
+export interface SelfUpdatingETARepository extends ETAGetterRepository {
+  /**
+   * Attach a event listener to the shuttle repository, listening to
+   * shuttle updates
+   */
+  startListeningForUpdates(): void;
+}