Enable Dependabot version updates

.github/dependabot.yml

@@ -0,0 +1,26 @@
+version: 2
+registries:
+  gradle-plugin-portal:
+    type: maven-repository
+    url: https://plugins.gradle.org/m2
+    username: dummy # Required by dependabot
+    password: dummy # Required by dependabot
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    groups:
+      github-actions:
+        patterns:
+        - "*"
+  - package-ecosystem: "gradle"
+    directory: "/"
+    registries:
+      - gradle-plugin-portal
+    schedule:
+      interval: "weekly"
+    groups:
+      gradle-dependencies:
+        patterns:
+        - "*"