Add dependabot config to open PRs for security updates

Author: asatwal

.github/dependabot.yml

@@ -0,0 +1,21 @@
+version: 2
+updates:
+  - package-ecosystem: bundler
+    directories:
+      - "/"
+      - "/gemfiles"
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    labels:
+      - dependencies
+      - ruby
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    labels:
+      - DevOps
+      - dependencies
+      - github_actions