Allow watching multiple words

[Erisa]

Allow watching for multiple words at once (e.g. "tailscale" and "tailnet"). To start with this would be an "or" operation so either one of the words being present will make a post eligible to trigger the webhook.

[bradfitz]

what does this mean? 😅

[Erisa]

Fleshed out the issue a bit, created to track some changes I threw together tonight