Can't bind listener for the "Shift" key only

[abuduba]

Currently it's not possible to bind listener for modifier keys only like:
keymage('shift', () => { console.log('Whoa!'); }

[brianreeve]

Consequently, it isn't possible to perform chords using modifier keys like shift shift.

[piranha]

Unfortunately, that would mean rewrite whole core. Ideally that's what needs to be done, but OTOH I don't use this library currently, so my motivation is pretty low :)