Update im.html

fix firefox os attach images, before only attachs video files

app/partials/im.html

@@ -147,7 +147,7 @@
                     <textarea ng-model="draftMessage.text" placeholder="Write a message..." class="form-control im_message_field"></textarea>
 
                     <div class="im_media_attach pull-right">
-                      <input type="file" class="im_media_attach_input" size="28" multiple="true" accept="image/x-png, image/png, image/gif, image/jpeg, video/*, audio/mpeg, audio/mp3" />
+                      <input type="file" class="im_media_attach_input" size="28" multiple="true" accept="image/*, video/*, audio/*" />
                       <i class="icon icon-camera"></i>
                     </div>