install.sh: ifconfig.io-API or querying the system hostname

[defautset]

Displaying the public IP address does not make sense in every installation scenario.

Please visit http://$(curl -4s https://ifconfig.io):8000 to get started ...

Locally, this would also work for me (e.g. querying the system hostname):

... or if you installed on a non-public network: http://$(uname -n):8000