[Wiki] NSFW should be for all triggers

[rachel]

Instead of just being for NSFW content, there should be a general purpose trigger[] tag which has a similar behavior to nsfw[], except it allows different templates / warning messages.

trigger[rape|hidden content]
trigger[racism|nazi memes]

Each of those example keywords would apply to a special template page that people could edit instead of the hardcoded text "NSFW content hidden (click to view)"