default not found to replace next 404

based off the dub.co/help not found

@Autumn-Ou is attempting to deploy a commit to the Elegance Team on Vercel.

A member of the Team first needs to authorize it.

Thanks for the PR! We'll need to add a proper 404 page that adds some context about what Dub does before we can merge this PR. Something like the existing placeholder pages for domains under the free plan (chatg.pt) could be a good starting point!

I can absolutely get to it in the next day or two the PR was mostly to get things started I'll change it to a draft, thanks!