Add allowed_networks config array

[NickBonet]

Hi there,

I noticed while trying to use WebDeck on a device in a separate VLAN (192.168.20.x), it could not connect as the check_local_network function explicitly only allows remote IPs from the the local network that WebDeck is located on. (192.168.1.x)

I modified check_local_network such that it checks if the remote IP matches any networks in the allowed_networks array located in the config JSON. It is an optional config array (left it empty in config_default.json), but if it exists, the check function will see if the remote IP matches any of the allowed network entries in the array before returning a 403 on requests.

This allowed me to access WebDeck from my device in the VLAN mentioned above, once I added the VLAN network to the allowed_networks array. Example of the array's usage:

    "allowed_networks": [
        "192.168.20.0/24"
    ]

[Lenochxd]

Really cool! I will add a setting in the settings to add IPs easily in the next update. Thanks!