Document Scala 3 support
<h4>Requirements</h4>
<p>
Log4j 2 Scala API is dependent on the Log4j 2 API, Scala runtime library and reflection.
- It currently supports Scala 2.10, 2.11 and 2.12. See <a href="../maven-artifacts.html#Scala_API">instructions</a>
+ It currently supports Scala 2.10, 2.11, 2.12, 2.13. Scala 3 support has been recently added.
+ See <a href="../maven-artifacts.html#Scala_API">instructions</a>
on including this in an SBT, Maven, Ivy, or Gradle project.
</p>
