Dependabot for actions

Signed-off-by: Hannes Achleitner <hannes.software@gmx.at>

.github/dependabot.yml

@@ -1,6 +1,10 @@
 version: 2
 updates:
-    -   package-ecosystem: gradle
+    -   package-ecosystem: "github-actions"
+        directory: "/" # Location of package manifests
+        schedule:
+            interval: "weekly"
+    -package-ecosystem: gradle
         directory: "/"
         schedule:
             interval: daily