docs(architecture): give example of libraries in TS and Dart (#2015)

Follow-up to
angular/angular.io#1972 (comment)

Author: chalin

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

@@ -120,7 +120,8 @@ block angular-library-modules
   `!{_at_angular}/core` is the primary Angular library from which we get most of what we need.
   <br clear="all">
 
-  There are other important Angular libraries too, such as `!{_at_angular}/common`, `!{_at_angular}/router`, and `!{_at_angular}/http`.
+  There are other important Angular libraries too, such as `!{_at_angular}/common`<span if-docs="ts">, 
+  `!{_at_angular}/http`</span> and `!{_at_angular}/router`.
   We import what we need from an Angular !{_library_module}.
 
 block angular-imports