Add a basic browser to mash that uses the navigation service.

services/navigation/manifest.json

 {
   "manifest_version": 1,
   "name": "exe:navigation",
   "display_name": "Navigation",
   "capabilities": {
+    "provided": {
+      "app":  [ "navigation::mojom::ViewFactory" ]
+    },
     "required": {
       "*": { "classes": [ "app" ] },
       "mojo:shell": { "classes": [ "shell:client_process", "shell:user_id", "shell:instance_name" ] }
     }
   }
 }