Support timer for similar keyboard chord distinction.

[cmaughan]

Is your feature request related to a problem? Please describe.
Sometimes we need to distinguish key chords based on timing; for example - CTRL+K is different to CTRL+KO - if there is a long enough pause after the K, then CTRL+K is executed. Or if CTRL+K is pressed then a key that isn't O.

Describe the solution you'd like
Add a key mapping timer to disambiguate the keystrokes. This might be the time to think about a remapping file too; though I am currently not enthused about making keymapping an option.

Describe alternatives you've considered
Currently we require a unique mapping. Currently CTRL+IO is alternative file, but I prefer KO.