add description

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

app/src/main/res/layout/toolbar_standard.xml

@@ -206,6 +206,7 @@
                     style="@style/Widget.AppTheme.Button.IconButton"
                     android:layout_width="48dp"
                     android:layout_height="48dp"
+                    android:contentDescription="@string/notification_icon_description"
                     app:cornerRadius="@dimen/button_corner_radius"
                     app:iconSize="20dp"
                     app:icon="@drawable/ic_notification"

app/src/main/res/values/strings.xml

@@ -1243,4 +1243,5 @@
     <string name="file_name_validator_error_forbidden_space_character_extensions">Filenames must not contain spaces at the beginning or end</string>
     <string name="sync">Sync</string>
     <string name="please_select_a_server">Please select a server…</string>
+    <string name="notification_icon_description">Unread notifications exist</string>
 </resources>