Adds a function `songwhip-lookup-url` which looks up the supplied URL
on Songwhip and copies the Songwhip link if a result was found.
This is bound to `s-s w` for convenience.
Change-Id: I3b529a058ee56f992942760910822490e6324259
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2002
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>