I just submitted a tiny Firefox addon for redirecting old.reddit.com and reddit.com to teddit.net. Seems like you were faster :-)

EDIT: Oh, I just realized you just added a rule to an existing addon. Here's a link to the addon I made, though it's not gonna be visible until it has been blessed by Mozilla: https://addons.mozilla.org/en-US/firefox/addon/reddit-to-ted...