Fix documentation of configuring extraDirectories for Gradle plugin
jib.extraDirectories = file('build/extra-directory') is one of the older syntax shown here, that is later deprecated in and removed in
@@ -361,7 +361,7 @@ mvn compile resources:copy-resources jib:build
The same can be accomplished in Gradle by using a `Copy` task. In your `build.gradle`:
```groovy
-jib.extraDirectories = file('build/extra-directory')
+jib.extraDirectories.paths = ['build/extra-directory']
task setupExtraDir(type: Copy) {
from file('build/generated/files')
