fix: redirect angular.io/docs to the latest ts docs (#3410)

* fix: redirect angular.io/docs to the latest ts docs
* Update firebase.json
* fix: redirect instead of rewrite requests to /docs
* squash: use absolute url

Author: IgorMinar

firebase.json

@@ -46,6 +46,11 @@
         "source": "/**/dart/**",
         "destination": "https://webdev.dartlang.org/angular?utm_campaign=dart_migration&utm_medium=redirect&utm_source=angular.io",
         "type": 301
+      },
+      {
+        "source": "/docs",
+        "destination": "https://angular.io/docs/ts/latest/",
+        "type": 301
       }
     ],
     "rewrites": [