Add Jenkinsfile for CI pipeline

Introduce a Jenkinsfile to automate the build process using Gradle. The pipeline consists of three stages: building with Gradle, archiving artifacts, and sending build notifications to Discord. This integration enhances the CI/CD workflow by ensuring consistent builds and timely notifications.

Jenkinsfile

@@ -0,0 +1,20 @@
+pipeline {
+    agent any
+    stages {
+        stage('Gradle') {
+            steps {
+                sh 'bash gradlew build'
+            }
+        }
+        stage('Archive') {
+            steps {
+                archiveArtifacts artifacts: 'build/libs/', followSymlinks: false
+            }
+        }
+        stage('discord') {
+            steps {
+                discordSend description: "Build: ${BUILD_NUMBER}", showChangeset: true, result: currentBuild.currentResult, title: currentBuild.fullProjectName, webhookURL: env.discordwebhook
+            }
+        }
+    }
+}