[Feature] Automatically select interface for `-b`

[GioF71]

Automatically find the local network interface and use it with the -b switch.
New variables:

ENABLE_AUTO_NETWORK_IFACE -> defaults to yes, disable with no
NETWORK_IFACE -> network interface selected by user
AUTO_NETWORK_IFACE_URL -> url used to set the local interface, defaults to 1.1.1.1