Add alt tags to close buttons

// FREEBIE

background.html

@@ -116,7 +116,7 @@
   </script>
   <script type='text/x-tmpl-mustache' id='attachment-preview'>
         <img src='{{ source }}' class='preview' />
-        <a class='x close' href='#'></a>
+        <a class='x close' alt='remove attachment' href='#'></a>
   </script>
   <script type='text/x-tmpl-mustache' id='hasRetry'>
     {{ messageNotSent }}
@@ -339,7 +339,7 @@
   <script type='text/x-tmpl-mustache' id='debug-log'>
     <div class='content'>
       <div>
-        <a class='x close' href='#'></a>
+        <a class='x close' alt='close debug log' href='#'></a>
         <h1> {{ title }} </h1>
         <p> {{ debugLogExplanation }}</p>
       </div>
@@ -356,7 +356,7 @@
   </script>
   <script type='text/x-tmpl-mustache' id='settings'>
     <div class='content'>
-      <a class='x close' href='#'></a>
+      <a class='x close' alt='close settings' href='#'></a>
       <h3>{{ notifications }}</h3>
       <p>{{ notificationSettingsDialog }}</p>
       <div>