Channel Restrictions improvement

18+ Channels Restriction [Multiple reasons instead NSFW only] In detail: To give discord members the freedom of writing why a channel has a 18+ tag, as example for "Venting channels", not everyone likes that kind of arguments so it could be usefull to explain members why a channel is 18+ [Normally putting a channel as 18+ says that channel is NSFW, there aren't other reasons that you can choose/write to replace the NSFW advertisement]