chore(sample): documented why autoresize is missing

sample/src/samples/input/textarea-sample.md

@@ -0,0 +1,9 @@
+##### Textareas don't autoresize
+
+The reason for that is there's a "hiddendiv" created on ```document.ready()``` to determine the height of the resized textarea.
+That hidden div doesn't exist anymore when the sample app creates real textareas ([see here](https://github.com/Dogfalo/materialize/blob/master/js/forms.js#L111)).
+After Aurelia takes control, it replaces the content of its container (meaning ```aurelia-app="main"```).
+
+<br/>
+
+The reference to ```hiddenDiv``` (a variable) is essentially broken once Aurelia kicks in. I'm not sure if there is any good workaround apart from creating such a div manually and outside of Aurelia scope.

sample/src/samples/input/textarea.html

@@ -16,14 +16,18 @@
             <div class="row">
               <ul md-tabs class="z-depth-1">
                 <li md-waves="color: primary;" class="col"><a class="active" href="#html">Html</a></li>
-                <li md-waves="color: primary;" class="col"><a class="active" href="#js">Javascript</a></li>
+                <li md-waves="color: primary;" class="col"><a href="#js">Javascript</a></li>
+                <li md-waves="color: primary;" class="col"><a href="#doc">Autoresize</a></li>
               </ul>
               <div id="html" class="z-depth-1">
                 <au-code language="markup" url="samples/input/textarea-sample.html"></au-code>
               </div>
               <div id="js" class="z-depth-1">
                 <au-code language="javascript" url="samples/input/basic-use-sample.js"></au-code>
               </div>
+              <div id="doc" class="z-depth-1" style="padding: 15px;">
+                <au-markdown url="samples/input/textarea-sample.md"></au-markdown>
+              </div>
             </div>
           </md-card>
         </div>