Add jenkins build

Jenkinsfile

@@ -0,0 +1,41 @@
+pipeline {
+    agent any
+    tools {
+        maven 'Maven 3'
+        jdk 'Java 8'
+    }
+    options {
+        buildDiscarder(logRotator(artifactNumToKeepStr: '5'))
+    }
+    stages {
+        stage ('Build') {
+            steps {
+                sh 'git submodule update --init --recursive'
+                sh 'mvn clean package'
+            }
+            post {
+                success {
+                    archiveArtifacts artifacts: 'target/*.jar', excludes: 'target/original-*.jar', fingerprint: true
+                }
+            }
+        }
+
+        stage ('Deploy') {
+            when {
+                branch "master"
+            }
+            steps {
+                sh 'mvn javadoc:jar source:jar deploy -DskipTests'
+            }
+        }
+    }
+
+    post {
+        always {
+            deleteDir()
+            withCredentials([string(credentialsId: 'geyser-discord-webhook', variable: 'DISCORD_WEBHOOK')]) {
+                discordSend description: "**Build:** [${currentBuild.id}](${env.BUILD_URL})\n**Status:** [${currentBuild.currentResult}](${env.BUILD_URL})\n\n[**Artifacts on Jenkins**](https://ci.nukkitx.com/job/GeyserConnect)", footer: 'NukkitX Jenkins', link: env.BUILD_URL, successful: currentBuild.resultIsBetterOrEqualTo('SUCCESS'), title: "${env.JOB_NAME} #${currentBuild.id}", webhookURL: DISCORD_WEBHOOK
+            }
+        }
+    }
+}