add dependabot (#426)

.github/dependabot.yml

@@ -0,0 +1,19 @@
+# Reference:
+# - https://docs.github.com/en/code-security/supply-chain-security/keeping-your-dependencies-updated-automatically/keeping-your-actions-up-to-date-with-dependabot
+# - https://docs.github.com/en/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file#groups
+
+version: 2
+updates:
+
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      # Check for updates to GitHub Actions every weekday
+      interval: "daily"
+    groups:
+      dependencies:
+        patterns:
+          - "*"
+    labels:
+      - "New: Pull Request"
+      - "Bot"