Update .getValue() - number of characters entered

inst/shiny-input-app/dev-shiny-input.Rmd

 ## Setup our input binding
 
 Now it's time to setup our input binding. Replace `FIXME` with `el.value`.
+(`r github_sha_link("85205fbcbb93ccb506558e62f73a8f0d6a88c83c")`)
+
+### Your Turn
+
+The `.value` of a `textarea` element 
+is a string containing the text inside the element.
+
+Update `.getValue()` to
+
+1. Return the number of characters the user has typed

inst/shiny-input-app/typing.js

     // your input. In this function, find or construct the value that will be
     // returned to Shiny. The ID of `el` is used for the inputId.
 
-    return el.value;
+    return el.value.length;
   },
   setValue: function(el, value) {
     // This method is used for restoring the bookmarked state of your input