Keyboard-specific remapping

[MatejKafka]

I'd like to use an extra keyboard as a "macro pad", by remapping some keys to the F13-F24 range, while still using another keyboard as a normal keyboard, with separate keymap.

As far as I understand, Interception supports this, but this feature is not exposed by Capsicain. Would it be possible to add it?

Something similar was already discussed in issue #3, but the solution there works around the problem instead of solving it. I'm willing to get my hands dirty and make a PR for this, but it will probably require quite substantial changes to the codebase, so I'd need to discuss it with you first and get some pointers. :)