Add project slogging to libraries

Author: jokade

index.md

@@ -131,6 +131,7 @@ All these testing frameworks cross-compile on the JVM and JS.
 * [Scala-Async](https://github.com/scala/async) (works out-of-box with Scala.js)
 * Scalaxy [Loops](https://github.com/ochafik/Scalaxy/tree/master/Loops) and [Streams](https://github.com/ochafik/Scalaxy/tree/master/Streams) (work out-of-box with Scala.js)
 * [jsext](https://github.com/jducoeur/jsext): utilities for developing facades and working with Futures
+* [slogging](https://github.com/jokade/slogging): a simple logging library with an API compatible to scala-logging (and slf4j)
 
 ## Skeletons