Convert shim to Typescript (#32)

ext/src/shim/cast/classes/Error.ts

@@ -0,0 +1,10 @@
+"use strict";
+
+// https://developers.google.com/cast/docs/reference/chrome/chrome.cast.Error
+export default class Error {
+    constructor (
+            public code: string
+          , public description: string = null
+          , public details: any = null) {
+    }
+};