User Interaction Consultation/Preference menu for readers

Brief Description
Give logged-out users a simplified personalization/preferences/beta menu just like Wikiwand does. So that they can increase the font size, pick a serif font, enable Hovercards etc.

Problem it solves

 * Logged-out users can currently not customize their reading experience or opt-in to certain features like logged-in readers can.
 * The tension between the community and the developers when community members to object to rolling out features or interface changes "against reader's wishes".

Details

 * Preferences could be stored as a cookie or in HTML local storage.
 * The menu should be much simpler than the interface currently is for logged-in users. Basically exactly like Wikiwand's menu.
 * Would be useful to also collect statistics about how many users are changing their settings from the default. (Don't just store the setting itself, but also log each change, so you can run some advanced analyses you didn't think of beforehand, afterwards.)
 * Ideally the settings would carry over once they create an account.
 * There should be one prominent button that lets readers easily switch between "Classic Wikipedia" and "Modern Wikipedia". This toggles a whole lot of preferences at once. Classic Wikipedia users have to opt-in for each new preference that gets added, Modern Wikipedia readers get them by default. (This aspect of the button should be clearly documented.)