Enable version updates for git submodules

Also, group dependabot PRs

Signed-off-by: Thomas Lauf <thomas.lauf@tngtech.com>

Author: lauft

.github/dependabot.yml

@@ -5,3 +5,14 @@ updates:
     directory: "/"
     schedule:
       interval: "weekly"
+    groups:
+      github-actions:
+        patterns: ["*"]
+  # Enable version updates for git submodules
+  - package-ecosystem: "gitsubmodule"
+    directory: "/"
+    schedule:
+      interval: "daily"
+    groups:
+      submodule:
+        patterns: ["*"]