docs(user-input): add link to Dart sample (#2175)

Contributes to #1598.

Author: chalin

public/docs/dart/latest/guide/user-input.jade

@@ -6,10 +6,12 @@ include ../_util-fns
   In this chapter we learn to bind to those events using the Angular
   event binding syntax.
 
+  <live-example>Run the live example</live-example>.
+
 :marked
   ## Binding to user input events
 
-  We can use Angular event bindings <!-- PENDING: link to ./template-syntax.html#event-binding -->
+  We can use [Angular event bindings](./template-syntax.html#event-binding)
   to respond to [any DOM event](https://developer.mozilla.org/en-US/docs/Web/Events).
 
   The syntax is simple. We surround the DOM event name with

public/docs/ts/latest/guide/user-input.jade

@@ -6,7 +6,7 @@ include ../_util-fns
   In this chapter we learn to bind to those events using the Angular
   event binding syntax.
 
-  <live-example>Run the live example</live-example>
+  <live-example>Run the live example</live-example>.
 
 :marked
   ## Binding to user input events