Add README example for package exclusion

See gh-114

Author: MALPI

README.adoc

@@ -136,6 +136,14 @@ For source formatting, add the `spring-javaformat-gradle-plugin` to your `build`
 The plugin adds `format` and `checkFormat` tasks to your project.
 The `checkFormat` task is automatically applied when running the standard Gradle `check` task.
 
+In case you want to exclude a package from being checked, for example if you generate sources, you can do this by adding following configuration:
+
+```
+tasks.withType(io.spring.javaformat.gradle.CheckTask) {
+    exclude "package/to/exclude"
+}
+```
+
 ==== Checkstyle
 To enforce checksyle conventions add the checkstyle plugin and include a dependency on `spring-javaformat-checkstyle`: