Use `/json/nodes` to discover more devices

[pille]

i'm using a VPN to connect to my WLED network.
therefore mDNS does not work to discover my devices.

to aid the process of importing my WLED devices, the app could query the API of already added devices to fetch their known neighbor nodes: /json/nodes.

this would improve setting up all devices from my local network, as it would only require me to add a single device manually.

[Moustachauve]

That's a good suggestion. I can't work on this for now as I am working on implementing new interfaces and adding software updates, but I can add this in the future :)