[Userscript] ConfusionGuesser

Version 1.6 patch-notes:

The script now also runs on the WK preview server

Added WaniKani — Log in as a @match so that the script also runs on that site.

Initially I didn’t plan to enable my script to run on the preview server, because I thought of the preview server as a place where each script author has to test their own script, and other users don’t need it enabled. But some people stated a different opinion, and I think there’s no harm in enabling it, so here you go.