Refactor: Add documentation for the Scastie configuration

Author: Dedelweiss

_overviews/scala3-scaladoc/settings.md

@@ -172,6 +172,14 @@ Which means:
 - all snippets in files under directory `my/path/f` should fail during compilation
 - all other snippets should compile successfully
 
+#### -scastie-configuration
+
+Add the scastie-configuration flag to the Scala compiler options to enable the Scastie configuration. This will allow you to include additional Sbt configuration for your Scastie snippets. For example, when you import external libraries into your snippets, you need to add the related dependencies.
+
+```
+"-scastie-configuration", """libraryDependencies += "org.apache.commons" % "commons-lang3" % "3.12.0""""
+```
+
 ##### -Ysnippet-compiler-debug
 
 Setting this option makes snippet compiler print the snippet as it is compiled (after wrapping).