Update Gradle demo to pass plugin dependencies into Manifest (#517)

demo_gradle/plugins/build.gradle

@@ -4,7 +4,8 @@ subprojects {
       attributes 'Plugin-Class': "${pluginClass}",
           'Plugin-Id': "${pluginId}",
           'Plugin-Version': "${archiveVersion}",
-          'Plugin-Provider': "${pluginProvider}"
+          'Plugin-Provider': "${pluginProvider}",
+          'Plugin-Dependencies': "${pluginDependencies}"
     }
   }