There is an open GitHub issue for this and it’s already been implemented in the Tailscale client, it’s really nice too as the DNS records are pushed out to the local DNS resolver on each Tailscale client, rather than being lookups to a separate server, so it’s super fast.
Unfortunately there aren’t any options for it on the Tailscale control panel, but if you use Headscale you can configure it and take advantage of it now.