build: add Spotless pre-commit hook

.pre-commit-config.yaml

@@ -0,0 +1,9 @@
+repos:
+  - repo: local
+    hooks:
+      - id: spotless-check
+        name: Spotless check
+        entry: ./gradlew spotlessCheck
+        language: system
+        pass_filenames: false
+        require_serial: true