Let dependabot only check for the composer file in webapp

Author: vmcj

.github/dependabot.yml

@@ -17,7 +17,7 @@ updates:
     allow:
         - dependency-type: "all"
   - package-ecosystem: "composer"
-    directory: "/"
+    directory: "/webapp"
     schedule:
       interval: "weekly"
     open-pull-requests-limit: 0