[CP-Sec] Enable dependabot for GitHub actions

Author: carlewis

.github/dependabot.yml

@@ -0,0 +1,13 @@
+version: 2
+updates:
+  # Enable version updates for Github Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "monthly"
+    groups:
+      github-actions:
+        patterns:
+          - "*"
+    reviewers:
+      - "codeplaysoftware/security-managers"