0.2.8

Only route local dns to active sessions (#60)

- Users may want to view other linkup sessions, or preview environments.
- With local-dns enabled, all these are routed to the local server where
the session does not exist
- Default dnsmasq to route to the public internet, but add special rules
for the active local session instead
- An annoying side-effect of this is still that linkup needs to be
started (for dnsmasq to be started) to view sessions, but 🤷