docs(webpack): add missing fake-async-test

closes #1571

Author: Foxandxss

public/docs/_examples/webpack/ts/config/karma-test-shim.js

@@ -8,6 +8,7 @@ require('zone.js/dist/zone');
 require('zone.js/dist/long-stack-trace-zone');
 require('zone.js/dist/jasmine-patch');
 require('zone.js/dist/async-test');
+require('zone.js/dist/fake-async-test');
 
 var appContext = require.context('../src', true, /\.spec\.ts/);