Feature: Toggle Autocompletion

Currently, autocompletion is enabled by default and there is no convenient way to disable it. Someone on the Discord wanted to, so I tracked down the appropriate console command. I think it would make more sense for it to be a toggle option in one of the menus (like "tags visible" is now). I'm happy to submit a pull request, but first I need to know which of the menus is appropriate for this.