add Jenkinsfile that triggers the frontend and backend pipeline

Jenkinsfile

@@ -0,0 +1,13 @@
+pipeline {
+    agent any
+    stages {
+        stage('Trigger Submodule Pipelines') {
+            steps {
+                script {
+                    build job: 'frontend-pipeline', wait: false
+                    build job: 'backend-pipeline', wait: false
+                }
+            }
+        }
+    }
+}