[schnierstein]

Added the option dracula-network-vpn-not-found-label in network_vpn.sh to let the user change what to display if no VPN is detected. Also added to the documentation.

I also had to add -eq 0 to the tailscale check because
With

    which -s tailscale > /dev/null
    tailscale_installed=$?
    if [ $tailscale_installed ] # <--- always true, even if tailscale not installed
      ...
    fi

So I changed the check to if [ $tailscale_installed -eq 0]