Replace _ with - in val names

[stevekrouse]

Underscores _ are not widely supported in subdomains, such as in in ChatGPT actions or Discord, Facebook or Clerk webhooks. We generally recommend removing underscores from val names to ensure compatibility.

This is our current plan from @tmcw:

[pomdtr]

<val>-<username> would be a much better convention than <username>-<val> imo

I can never find my val.town websites using the chrome/arc omnibar, because they prioritize the start of the hostname in their matching algorithm.