Binding multiple combinations does not work as expected (or the callback needs an extra parameter)

[ContraTrouble]

Let's say I have the letters "a", "b", and "c" and want to bind a different callback for each unique combination on keyup (think a "chord" in music where you press multiple keys at the same time).

For simplicity let's have only 3 combinations:

• ["a", "b"] (the one I will press)
• ["a", "c"]
• ["c", "b"]

If I bind the above 3 sequences, when I press and hold "a" and "b", the callback will be called twice, for:

• ["a", "c"] - it seems to pick a combination where the 1st letter matches the 1st letter in the bound sequence
• ["c", "b"] - ditto - picks a combination where the 2nd letter matches the 2nd letter in the bound sequence

What I need is for it to trigger only for ["a", "b"] which are the 2 keys I actually pressed.

In the title of the issue, when I said "or the callback needs an extra parameter" I meant that instead of just passing the keyboard event as an argument, the library could pass the actual sequence (e.g. ["a", "c"]), and then I'd be able to filter out the "bogus" combinations. This will not fix my issue (now), because as I explained, the callback for the ["a", "b"] combination that I'm expecting to be called is not called at all.

I'm not in a hurry (can wait a couple of months), but if you're too busy or don't recognize this as something that's needed, please comment on the issue, and I'll either fork it, or create a PR (if you think that's useful).

Thanks!