Manage Gradle Enterprise plugins with Dependabot (#5342)

* Add dependabot configuration to monitor Gradle plugins

* Restrict registries to Gradle Plugin Portal

Author: jprinet

.github/dependabot.yml

@@ -1,10 +1,25 @@
 version: 2
+registries:
+  gradle-plugin-portal:
+    type: maven-repository
+    url: https://plugins.gradle.org/m2
+    username: dummy # Required by dependabot
+    password: dummy # Required by dependabot
 updates:
   - package-ecosystem: "gradle"
     directory: "/core"
     schedule:
       interval: "monthly"
     open-pull-requests-limit: 10
+  - package-ecosystem: "gradle"
+    directory: "/"
+    allow:
+      - dependency-name: "com.gradle*"
+    registries:
+      - gradle-plugin-portal
+    schedule:
+      interval: "monthly"
+    open-pull-requests-limit: 10
 
 # Explicit entry for each module
   - package-ecosystem: "gradle"