Update Dependabot Grouping (#493)

Now dependabot should create a single PR for all the dependencies. [Example PR](SentryMan/avaje-javalin-api-example#50)

Author: SentryMan

.github/dependabot.yml

@@ -3,13 +3,16 @@ updates:
   - package-ecosystem: "maven"
     directory: "/"
     schedule:
-      interval: "weekly"
+      interval: weekly
     open-pull-requests-limit: 10
+    groups:
+      dependencies:
+        patterns:
+        - "*"
     labels:
       - "dependencies"
     target-branch: "master"
 
-
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule: