Add Jenkins support

Jenkinsfile

@@ -0,0 +1,37 @@
+pipeline {
+    agent {
+        docker {
+            image 'gradle:4.10.3-jdk8-alpine'
+            args '-v gradle-cache:/home/gradle/.gradle'
+        }
+    }
+
+    stages {
+        stage('Clean') {
+            steps {
+                dir('build/libs') {
+                    deleteDir()
+                }
+            }
+        }
+
+        stage('Build') {
+            environment {
+                MAVEN_SECRETS_FILE = credentials('maven-secrets')
+
+                JARSIGN_KEYSTORE_FILE = credentials('gilded-games-jarsign-keystore')
+                JARSIGN_SECRETS_FILE = credentials('gilded-games-jarsign-secrets')
+            }
+
+            steps {
+                sh 'gradle build --no-daemon'
+            }
+        }
+    }
+
+    post {
+        success {
+            archiveArtifacts artifacts: 'build/libs/*.jar', fingerprint: true
+        }
+    }
+}