Fix SpotlessPredeclareExtension for kotlin users (#1084)

Author: nedtwigg

plugin-gradle/CHANGES.md

@@ -6,6 +6,8 @@ We adhere to the [keepachangelog](https://keepachangelog.com/en/1.0.0/) format (
 ### Added
 * 🎉🎉🎉 [**IntelliJ plugin**](https://plugins.jetbrains.com/plugin/18321-spotless-gradle) thanks to [@ragurney](https://github.com/ragurney) 🎉🎉🎉
 * Added support for the [palantir-java-format](https://github.com/palantir/palantir-java-format) Java formatter ([#1083](https://github.com/diffplug/spotless/pull/1083)).
+### Fixed
+* Register `spotlessPredeclare` extension with type `SpotlessExtensionPredeclare` instead of the same `SpotlessExtension` as `spotless` so that Kotlin users can use `configure<SpotlessExtensionPredeclare>` ([#1084](https://github.com/diffplug/spotless/pull/1084)).
 
 ## [6.1.2] - 2022-01-07
 ### Fixed

plugin-gradle/src/main/java/com/diffplug/gradle/spotless/SpotlessExtension.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2021 DiffPlug
+ * Copyright 2016-2022 DiffPlug
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -275,6 +275,6 @@ public void predeclareDeps() {
 	}
 
 	protected void predeclare(GradleProvisioner.Policy policy) {
-		project.getExtensions().create(SpotlessExtension.class, EXTENSION_PREDECLARE, SpotlessExtensionPredeclare.class, project, policy);
+		project.getExtensions().create(SpotlessExtensionPredeclare.class, EXTENSION_PREDECLARE, SpotlessExtensionPredeclare.class, project, policy);
 	}
 }