Add support for webln.keysend calls

[bumi]

webln was extended by a keysend method: https://github.com/joule-labs/webln/pull/42

It would be great if the blixt lightning browser also supports this webln call. keysend is the main method used for podcasting 2.0 payments (see "The "podcast:value" Specification") and more related web applications are build.

Documentation: https://www.webln.guide/building-lightning-apps/webln-reference/webln.keysend

[hsjoberg]

Hey @bumi! I have already opened an issue about it here #445.

[bumi]

ohh, sorry. how did I miss that! thanks

[hsjoberg]

No worries