chore: configure license to java files

Author: simschla

build-logic/src/main/groovy/buildlogic.spotless-java-conventions.gradle

@@ -8,5 +8,6 @@ spotless {
         formatAnnotations()
         removeUnusedImports()
         importOrder('java|javax', 'org', 'com', 'com.diffplug', '', '\\#')
+        licenseHeaderFile rootProject.file('gradle/spotless.license')
     }
 }

gradle/spotless.license

@@ -0,0 +1,15 @@
+/*
+ * Copyright $YEAR DiffPlug
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */