add dependabot config

.github/dependabot.yml

@@ -0,0 +1,24 @@
+version: 2
+updates:
+  - package-ecosystem: "maven"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+      timezone: "UTC"
+    groups:
+      all: # one PR for all dependencies
+        patterns:
+          - "*"
+
+  - package-ecosystem: "github-actions"
+    directory: "/" # even for `.github/workflows`
+    schedule:
+      interval: "monthly"
+    groups:
+      all: # one PR for all actions
+        patterns:
+          - "*"
+    labels:
+      - "misc:ci"