fix(dependabot): specify Maven as package ecosystem in dependabot.yml

- Set `package-ecosystem` to `maven` to enable dependency updates for pom.xml
- Ensure Dependabot checks for updates in the root directory `/`
- Schedule weekly dependency updates
- Limit open pull requests to 5 to prevent spam

Author: Piotr Kubicki

.github/dependabot.yml

@@ -5,7 +5,8 @@
 
 version: 2
 updates:
-  - package-ecosystem: "" # See documentation for possible values
-    directory: "/" # Location of package manifests
+  - package-ecosystem: "maven"  # Specify Maven as the package ecosystem
+    directory: "/"  # Root directory where pom.xml is located
     schedule:
-      interval: "weekly"
+      interval: "weekly"  # Dependabot will check for updates every week
+    open-pull-requests-limit: 5  # Optional: Limit the number of open PRs from Dependabot