ScalaJS Implementation for our slf4j-api wrapper.

[ChristopherDavenport]

This would mean backporting some of the internals of slf4j to scalajs so this works as well. Some previous art exists in other scala logging libraries.

[cquiroz]

Couldn't this be done with just log4s?

[ChristopherDavenport]

https://github.com/ChristopherDavenport/log4cats-log4s - Log4s already has a scalajs backend, but the intermediate layer is unnecessary for this abstraction.