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.
 * 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.)