chore: enable dependabot version updates of github-actions yaml files (#1930)

Author: v1v

.github/dependabot.yml

@@ -8,8 +8,24 @@ updates:
     # Check for updates once a week
     schedule:
       interval: "weekly"
+      day: "sunday"
+      time: "22:00"
     reviewers:
       - "elastic/apm-agent-python"
     ignore:
       - dependency-name: "urllib3" # ignore until lambda runtimes use OpenSSL 1.1.1+
         versions: [">=2.0.0"]
+
+  # GitHub actions
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    reviewers:
+      - "elastic/observablt-ci"
+    schedule:
+      interval: "weekly"
+      day: "sunday"
+      time: "22:00"
+    groups:
+      github-actions:
+        patterns:
+          - "*"