The addition of further keyboard layouts would otherwise pollute the
config/ directory too much.
Caution: When updating Sculpt OS, don't reuse your existing
config/event_filter file unmodified! You need to replace the chargen
includes, pointing to the new location, e.g.,
<include rom="en_us.chargen"/>
<include rom="special.chargen"/>
must be changed to
<include rom="keyboard/en_us"/>
<include rom="keyboard/special"/>
Issue #4055