NSFW warning when first entering the Atlas

[onceuponaban]

Describe the solution

This year's iteration of /r/place is notable for including a piece of artwork that is rather blatantly NSFW. I am of course referring to the version of Shego that made it to the final canvas... or at least what Reddit decided was the final canvas after their own carelessness triggered a printer bot apocalypse that pretty much invalidated the last couple of hours of the event.

Inexplicably, Reddit seemingly didn't do any edit to this section before publishing the canvas despite using their moderation tools during the event itself to censor the NSFW part, which leads to a concern that the Atlas could possibly get in trouble for featuring at least one NSFW artwork in the default view.

Censoring the artwork ourselves is obviously out of the question (and would set a precedent I don't think we want to, namely opening up the possibility of censoring more NSFW sections of the canvas within the timeline), so I believe that it would be appropriate that on first visiting the Atlas, the website displays a warning infobox about the existence of NSFW artwork on the canvas, and to proceed with caution. This should alleviate any problem.