support schemaless urls

[alexwennerberg]

I use protocol-relative URLs sometimes, such as

//google.com

instead of

https://google.com

Is there any way this library could be modified to include these URLs? Maybe as an optional configuration?

See
https://datatracker.ietf.org/doc/html/rfc3986#section-4.2

[mre]

See #17. The PR is not being worked on right now, but you might want to look into the remaining issues mentioned there.