Create a LDK node connection QR code format

[Bosch-0]

Hello,

It would be handy if their was a simple way to connect to an LDK node by scanning a QR code, similar to LND connect and the WIP by @opnoms here for C-lightning.

Eclair issue

[TheBlueMatt]

Hmm, I don't think this kind of thing belongs in LDK - LDK is not a lightning node itself, but a toolkit to build a custom lightning node with any features you want. Our API already exposes enough information to construct such a QR code, and it's up to LDK users (ie the authors of node software) if such a feature makes sense to them.