Add dependabot

Without this patch, our deps will have to be manually maintained.

This should fix it.

.github/dependabot.yml

+version: 2
+updates:
+  # Maintain dependencies for GitHub Actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"
+  # Maintain dependencies for gomod
+  - package-ecosystem: "gomod"
+    directory: "/"
+    schedule:
+      interval: "daily"