chore(gh): add dependabot (#1423)

.github/dependabot.yml

@@ -0,0 +1,16 @@
+---
+version: 2
+updates:
+  # Maintain dependencies for GitHub Actions.
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      # Check for updates to GitHub Actions every week.
+      interval: "weekly"
+
+  # Maintain dependencies for Go modules
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      # Check for updates to Go modules every week.
+      interval: "weekly"