Add basic Backbone type definitions

ts/types/backbone/Collection.ts

@@ -0,0 +1,11 @@
+/**
+ * @prettier
+ */
+import { Model } from './Model';
+
+export interface Collection<T> {
+  models: Array<Model<T>>;
+  // tslint:disable-next-line no-misused-new
+  new(): Collection<T>;
+  fetch(options: object): JQuery.Deferred<any, any, any>;
+}

ts/types/backbone/Model.ts

@@ -0,0 +1,7 @@
+/**
+ * @prettier
+ */
+
+export interface Model<T> {
+  toJSON(): T;
+}