A way to wrap an existing KeyMapping into Kuma

[BlayTheNinth]

e.g.

ManagedKeyMapping result = Kuma.manageKeyMapping(keyMapping)
    .withModifiers(KeyModifiers.of(KeyModifier.CONTROL))
    .handleScreenInput((event) -> {
    })
    .build();

i.e. most of the builder methods could be made available, apart from
id, category, name, defaultBinding (only modifiers), skipRegistration

This would allow

1. for easier adoption of Kuma without having to rewrite existing Key Mapping registration
2. for wrapping Kuma around existing key mapping registrars
3. for the eventually planned optional standalone Kuma mod to Kuma-fy all key mappings