Jenkinsfile: use gerrit-ci-library pipeline for plugin validation

Change-Id: I2677099818336155599154a9ed5b55f9d1b84441

Jenkinsfile

diff --git a/Jenkinsfile b/Jenkinsfile
new file mode 100644
index 0000000..f008749
--- /dev/null
+++ b/Jenkinsfile
@@ -0,0 +1,2 @@
+pluginPipeline(formatCheckId: 'gerritforge:multi-site-format-47168e90078b0b3f11401610930e82830e76bff7',
+               buildCheckId: 'gerritforge:multi-site-47168e90078b0b3f11401610930e82830e76bff7')