build(main.ts): add hammer.js (#55)

Add hammer.js for touch gesture support.

Fixes #54

src/main.ts

@@ -7,6 +7,8 @@
 import { enableProdMode } from '@angular/core';
 import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
 
+import 'hammerjs';
+
 import { AppModule } from './app/app.module';
 import { environment } from './environments/environment';