update indentation (4 spaces -> 2 spaces)

src/OpenerButton.vue

@@ -15,11 +15,11 @@ 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"></button>
+  <button class="side-menu-opener"></button>
 </template>
 
 <script>
 export default {
-    name: 'OpenerButton',
+  name: 'OpenerButton',
 }
 </script>