Add chat and mailing list links to README and Contributing guidelines (…

…#354)

* Add a Gitter chat link to README

* Add contact links to CONTRIBUTING guidelines

CONTRIBUTING.md

@@ -1,5 +1,7 @@
 # Contributing to Jenkinsfile Runner
 
+[![Gitter](https://badges.gitter.im/jenkinsci/jenkinsfile-runner.svg)](https://gitter.im/jenkinsci/jenkinsfile-runner)
+
 This page provides information about contributing code to the Jenkinsfile Runner codebase.
 
 ## Getting started
@@ -19,6 +21,15 @@ This page provides information about contributing code to the Jenkinsfile Runner
 This page provides basic information about building and testing Jenkinsfile Runner.
 In case you are more interested in details and in the architecture, see the [Developer Documentation](./docs/developer/README.md).
 
+## Contacts
+
+If you have any questions or need help, please use the following channels:
+
+* [Gitter Chat](https://gitter.im/jenkinsci/jenkinsfile-runner) - for JFR usage and development questions
+* [Jenkins Cloud Native SIG](https://www.jenkins.io/sigs/cloud-native/) channels: mailing lists, chats, meetings
+* [Jenkins Developer Mailing list](https://groups.google.com/d/forum/jenkinsci-dev) - for JFR development questions
+
+
 ## Building
 
 The build flow for Jenkinsfile Runner is built around Maven and Docker.

README.md

@@ -3,6 +3,7 @@
 [![GitHub release (latest by date including pre-releases)](https://img.shields.io/github/v/release/jenkinsci/jenkinsfile-runner?include_prereleases&label=changelog)](https://github.com/jenkinsci/jenkinsfile-runner/releases/latest)
 [![Docker Pulls](https://img.shields.io/docker/pulls/jenkins/jenkinsfile-runner?label=docker%20pulls%20%28vanilla%29)](https://hub.docker.com/r/jenkins/jenkinsfile-runner)
 [![GitHub contributors](https://img.shields.io/github/contributors/jenkinsci/jenkinsfile-runner)](https://github.com/jenkinsci/jenkinsfile-runner/graphs/contributors)
+[![Gitter](https://badges.gitter.im/jenkinsci/jenkinsfile-runner.svg)](https://gitter.im/jenkinsci/jenkinsfile-runner)
 
 Jenkinsfile Runner packages Jenkins pipeline execution as a command line tool or as a Docker image.
 Target use cases include but not limited to: