chore(dependabot): add config.yml

This adds dependabot integration which is integrated in GitHub.
Doing so will automatically create pull requests (including changelog/commits) whenever a go dependency is updated or the golang Docker image is updated.

.dependabot/config.yml

@@ -0,0 +1,9 @@
+version: 1
+update_configs:
+  - package_manager: "docker"
+    directory: "/"
+    update_schedule: "daily"
+  
+  - package_manager: "go:modules"
+    directory: "/"
+    update_schedule: "daily"