Fix keyboard shortcuts not working in CryptDrive

www/drive/inner.html

@@ -11,7 +11,7 @@
 <body>
     <div id="toolbar" class="toolbar-container"></div>
     <div id="driveToolbar"></div>
-    <div class="app-container">
+    <div class="app-container" tabindex="0">
         <div id="tree">
         </div>
         <div id="content">