add Jenkinsfile to enable separate CI for pull requests

Jenkinsfile

@@ -0,0 +1,29 @@
+pipeline {
+    agent any
+
+    stages {
+        stage('phpunit') {
+            steps {
+                sh """
+                docker run --rm \
+                    --volumes-from jenkins-docker_app_1 \
+                    --workdir ${env.WORKSPACE} \
+                    php:8.1-cli \
+                    php ./vendor/bin/phpunit
+                """
+            }
+        }
+        stage('phpstan') {
+            steps {
+                sh """
+                # php -d memory_limit=-1 ....
+                docker run --rm \
+                    --volumes-from jenkins-docker_app_1 \
+                    --workdir ${env.WORKSPACE} \
+                    php:8.1-cli \
+                    php -d memory_limit=-1 ./vendor/bin/phpstan --memory-limit=2G
+                """
+            }
+        }
+    }
+}