[strings] Add contentDescription to bottom buttons for accessibility

Signed-off-by: Alex Gorichev <Alex.Gorichev@protonmail.com>

android/res/layout/map_buttons_help.xml

@@ -4,5 +4,6 @@
   xmlns:app="http://schemas.android.com/apk/res-auto"
   android:id="@+id/help_button"
   style="@style/MwmWidget.MapButton.Square"
+  android:contentDescription="@string/help"
   app:shapeAppearanceOverlay="@style/MwmWidget.MapButton.Square"
   android:src="@drawable/ic_question_mark" />

android/res/layout/map_buttons_menu.xml

@@ -4,5 +4,6 @@
   xmlns:app="http://schemas.android.com/apk/res-auto"
   android:id="@+id/menu_button"
   style="@style/MwmWidget.MapButton.Square"
+  android:contentDescription="@string/menu"
   app:shapeAppearanceOverlay="@style/MwmWidget.MapButton.Square"
   android:src="@drawable/ic_menu_open" />

data/strings/strings.txt

@@ -5000,6 +5000,14 @@
     zh-Hans = 在地图上查看
     zh-Hant = 在地圖上查看
 
+  [menu]
+    comment = Menu button
+    tags = android
+    en = Menu
+    pl = Menu
+    ru = Меню
+    uk = Меню
+
   [website]
     comment = Text in menu
     tags = android,ios