ci: Add dependabot

.github/dependabot.yml

@@ -0,0 +1,20 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    labels:
+      - "dependencies"
+  - package-ecosystem: "gradle"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    labels:
+      - "dependencies"
+  - package-ecosystem: "pub"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    labels:
+      - "dependencies"