Module i_slint_common::key_codes

This module is meant to be included by different crate and each crate must define the macro for_each_keys

The key code comes from https://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/CORPCHAR.TXT the names comes should match with https://www.w3.org/TR/uievents-key/#named-key-attribute-values,