add accessibility to open and close buttons (#311)

refactor the way to focus apps when the menu is opened (#301)

src/OpenerButton.vue

@@ -15,7 +15,9 @@ You should have received a copy of the GNU Affero General Public License
 along with this program. If not, see <http://www.gnu.org/licenses/>.
 -->
 <template>
-  <button class="side-menu-opener" :arial-label="label"></button>
+  <button class="side-menu-opener" :arial-label="label">
+    <span v-text="label"></span>
+  </button>
 </template>
 
 <script>
@@ -23,7 +25,7 @@ export default {
   name: 'OpenerButton',
   data() {
     return {
-      label: t('side_menu', 'Toggle menu'),
+      label: t('side_menu', 'Toggle the menu'),
     }
   }
 }