normalize keycodes

[pmp-p]

so keyboard map layout have no influence on keys placement.

https://developer.mozilla.org/en-US/docs/Web/API/UI_Events/Keyboard_event_code_values

http://ps-2.kev009.com/wisclibrary/aix52/usr/share/man/info/en_US/a_doc_lib/aixkybd/kybdtech/Key.htm

[pmp-p]

which would be event.code in javascript