Add close tab confirmation, Ctrl + W, close button about rogueworld HOT 2 CLOSED

I did some investigation and found that this can be resolved by using the onbeforeunload event to display a pop up message when the player attempts to refresh the page or close the tab.

However, it seems like most modern browsers have disabled custom pop up messages in order to prevent spoofing attacks:

• https://stackoverflow.com/questions/38879742/is-it-possible-to-display-a-custom-message-in-the-beforeunload-popup

• https://stackoverflow.com/questions/37782104/javascript-onbeforeunload-not-showing-custom-message

from rogueworld.

If possible, it might be an alternative to just show the create account panel on the onbeforeunload event, as if they had pressed on the top right button directly. The message content doesn't necessarily need to be within the browser's own close confirmation box.

ACs updated.

from rogueworld.