docs(getting-started): mention importing hammer in same file as bootstrap (#6225)

* docs(hammerjs): new import location for Universal

As mentioned in #308, if hammerjs is imported in AppModule, Universal server-side rendering will fail as hammerjs is a browser specific library using window, document... So it must be imported in browser entry point src/main.ts instead.

* docs(hammerjs): new import location for Universal

As mentioned in #308, if hammerjs is imported in AppModule, Universal server-side rendering will fail as hammerjs is a browser specific library using window, document... So it must be imported in browser entry point src/main.ts instead.

Author: cyrilletuzi

guides/getting-started.md

@@ -113,7 +113,7 @@ To install via npm, use the following command:
 npm install --save hammerjs
 ```
 
-After installing, import it on your app's root module.
+After installing, import it on your app's entry point (e.g. `src/main.ts`).
 ```ts
 import 'hammerjs';
 ```