Add arpeggios

[alice-i-cecile]

Needs:

• internal state on InputMap (related to Add configurable grace period for detecting inputs #48)
• timeout detection

[johanhelsing]

How will arpeggios work? will it be able to say that

• ctrl down, alt down, p down should trigger the action
• alt down, ctrl down, p down should trigger the action
• p down, ctrl down, alt down should not trigger the action

Or maybe I'd need to add two arpeggios? one for alt+ctrl and one for ctrl+alt?

[alice-i-cecile]

Or maybe I'd need to add two arpeggios? one for alt+ctrl and one for ctrl+alt?

This is the idea. I intend to add builder methods to make that easy, along with a reasonable "modifier key" setup which does this automatically.

If there were likely to be arpeggios of more than three inputs, with this sort of branching logic, I'd add a graph-builder API, but I think that's dramatically over-engineering here 😄

[alice-i-cecile]

Arpeggios should chain as long as there no gap between adjacent inputs.

[alice-i-cecile]

Closing in favor of #485.