Add link to GitHub in the quickstart page (#2949)

So you don't need to manually select the link with your mouse to view
these examples.

Author: Nikitf777

docs/guide/02-quickstart.md

@@ -12,7 +12,7 @@ Started].
 ## Running Examples
 
 The absolute fastest way to start experimenting with Rocket is to clone the
-Rocket repository and run the included examples in the `examples/` directory.
+[Rocket repository](https://github.com/rwf2/Rocket) and run the included examples in the `examples/` directory.
 For instance, the following set of commands runs the `hello` example:
 
 ```sh