Add configuration option to bind to a specific network adapter

[andrew-rosca]

On machines with multiple network adapters, it would be useful to be able to select which adapter to bind to and update the DNS entry for.

For example, if I have a physical network adapter and a VPN connection, I may want to update DuckDNS for the physical adapter, but by default it will instead retrieve and update the IP address of the VPN connection (because/if that's the network adapter with the highest priority)

[andrew-rosca]

@JozefJarosciak I made some modifications to your code to support what I am describing above. Not fully tested yet but I'd like to get your feedback before I proceed further. Can I commit to a separate branch so we can discuss?