Update README: Governance, Adopters and more links (#4836)

* Update README: Governance, Adopters and more links

* Apply suggestions from code review
Co-authored-by: NDaniel Beck <1831569+daniel-beck@users.noreply.github.com>

* Update README.md
Co-authored-by: NTim Jacomb <timjacomb1+github@gmail.com>
Co-authored-by: NDaniel Beck <1831569+daniel-beck@users.noreply.github.com>
Co-authored-by: NTim Jacomb <timjacomb1+github@gmail.com>

README.md

@@ -5,7 +5,7 @@
 [![Docker Pulls](https://img.shields.io/docker/pulls/jenkins/jenkins.svg)](https://hub.docker.com/r/jenkins/jenkins/)
 
 In a nutshell, Jenkins is the leading open-source automation server. 
-Built with Java, it provides over 1600 [plugins](https://plugins.jenkins.io/) to support automating virtually anything, 
+Built with Java, it provides over 1700 [plugins](https://plugins.jenkins.io/) to support automating virtually anything, 
 so that humans can actually spend their time doing things machines cannot.
 
 # What to Use Jenkins for and When to Use It
@@ -26,13 +26,27 @@ Non-source downloads such as WAR files and several Linux packages can be found o
 Our latest and greatest source of Jenkins can be found on [GitHub]. Fork us!
 
 # Contributing to Jenkins
+
 Follow the [contributing guidelines](CONTRIBUTING.md) if you want to propose a change in the Jenkins core.
+For more information about participating in the community and contributing to the Jenkins project,
+see [this page](https://www.jenkins.io/participate/).
 
-# Maintainers guidelines
 Documentation for Jenkins core maintainers is in the [maintainers guidelines](docs/MAINTAINERS.adoc).
 
 # News and Website
-All information about Jenkins can be found on our [website]. Follow us on Twitter [@jenkinsci].
+
+All information about Jenkins can be found on our [website].
+Follow us on [Twitter](https://twitter.com/jenkinsci) or [LinkedIn](https://www.linkedin.com/company/jenkins-project/).
+
+# Governance
+
+See the [Jenkins Governance Document](https://www.jenkins.io/project/governance/) for information about the project's open governance, our philosophy and values, and development practices.
+Jenkins Code of Conduct can be found [here](https://www.jenkins.io/project/conduct/).
+
+# Adopters
+
+Jenkins is used by millions of users and thousands of companies.
+See [adopters](https://www.jenkins.io/project/adopters/) for the list of Jenkins adopters and their success stories.
 
 # License
 Jenkins is **licensed** under the **[MIT License]**.
@@ -43,4 +57,3 @@ Jenkins is **licensed** under the **[MIT License]**.
 [Mirrors]: http://mirrors.jenkins-ci.org
 [GitHub]: https://github.com/jenkinsci/jenkins
 [website]: https://jenkins.io/
-[@jenkinsci]: https://twitter.com/jenkinsci