fix(updates): prevent problems updating to latest version

service-workers seem to have a problem no finding the relevant resources on es2015
angular/angular-cli#15259 (comment)

Author: sleidig

tsconfig.json

@@ -9,7 +9,7 @@
     "moduleResolution": "node",
     "emitDecoratorMetadata": true,
     "experimentalDecorators": true,
-    "target": "es2015",
+    "target": "es5",
     "downlevelIteration": true,
     "types": [ "node", "jasmine" ],
     "typeRoots": [ "../node_modules/@types" ],