REQ: Render QR code for sharing

[xxxserxxx]

Wormhole William mobile can scan a QR code to receive a file; the complimentary function is to render a QR code for a share that another instance of Wormhole William can scan to receive.

[psanford]

Yup, I wanted this just the other day. I'll up prioritize it.

[xxxserxxx]

If you procrastinate enough, I may send a PR. I can probably figure out goui enough for this one. But I did want a ticket to hang it off of.

[psanford]

I'd happily take a PR for this.