[UX] Allow keyboard layout selection (#5318)

Fixes <https://github.com/koreader/koreader/issues/3998>.

This isn't quite what I want but I've been letting this slip for
too long due to fancier keyboard interaction concepts.

frontend/ui/elements/common_settings_menu_table.lua

@@ -210,6 +210,10 @@ if Device:isAndroid() then
 end
 
 if Device:isTouchDevice() then
+    common_settings.keyboard_layout = {
+        text = _("Keyboard layout"),
+        sub_item_table = require("ui/elements/menu_keyboard_layout"),
+    }
     common_settings.taps_and_gestures = {
         text = _("Taps and gestures"),
     }