Add lightning address payment

[ShahanaFarooqui]

Add support for payment to a lightning address.

Reference: https://lightningaddress.com/

[kristapsk]

This could be done as a script or plugin. I had a plan to write one for cln-scripts, but maybe will put that on hold if there are plans to include this in CLN itself.

[rustyrussell]

@kristapsk I was going to write a plugin called "xpay". Want to collaborate?

[tonyaldon]

@rustyrussell I would like to collaborate with you on "xpay" plugin (I remember you talked about it in a CLN meeting). Is it possible? Did you already draft something?

[kristapsk]

@rustyrussell Missed your comment initially (too much spam in mailbox), I would be interested, yes.

[tonyaldon]

@kristapsk As you didn't reply, I assumed you wasn't interested :) Anyway, I'll be working on something else.