docs(router): fix missing anchor id (#2817)

The link *Importing from the router library* (https://angular.io/docs/ts/latest/guide/router.html#import) does not work.

I supposed that this was the corresponding section to be linked to.

Author: johnjacobkenny

public/docs/ts/latest/guide/router.jade

@@ -399,6 +399,7 @@ a#base-href
   :marked
     We should only need this trick for the live example, not production code.
 
+a#import
 :marked
   ### Configure the routes for the Router