Log number of keystrokes, mouse delta

[ErikBjare]

One aspect of this seems difficult: We'd want to log the number of keystrokes per window, so that'd mean we have to couple the keycount event duration to the window event somehow.

Not sure how to do this without tying it into the window watcher one way or another. A slightly depraved solution would be to poll/subscribe to the window events and create a new entry where appropriate. I can imagine a bunch of solutions involving the server as well but I'd rather not just for this specific case.