chore: update dependabot to weekly Sunday schedule (#12539)

chore: add standardized dependabot config

Weekly Sunday 22:00 UTC, 5 PR limit per ecosystem, minor+patch grouped.

Signed-off-by: Thomas Müller <1005065+DeepDiver1975@users.noreply.github.com>

Author: DeepDiver1975

.github/dependabot.yml

@@ -1,12 +1,15 @@
-# To get started with Dependabot version updates, you'll need to specify which
-# package ecosystems to update and where the package manifests are located.
-# Please see the documentation for all configuration options:
-# https://docs.github.com/code-security/dependabot/dependabot-version-updates/configuration-options-for-the-dependabot.yml-file
-
 version: 2
 updates:
-  # Maintain dependencies for GitHub Actions
-  - package-ecosystem: "github-actions"
+  - package-ecosystem: github-actions
     directory: "/"
     schedule:
-      interval: "weekly"
+      interval: weekly
+      day: sunday
+      time: '22:00'
+      timezone: Etc/UTC
+    open-pull-requests-limit: 5
+    groups:
+      minor-and-patch:
+        update-types:
+          - minor
+          - patch