Install Tekton on the cluster

[siamaksade]

Add an action to be able to install Tekton on a cluster which doesn't have Tekton installed.

Kubernetes:
https://github.com/tektoncd/pipeline/blob/master/docs/install.md
https://github.com/tektoncd/triggers/blob/master/docs/install.md

OpenShift:
Installing the OpenShift Pipelines Operator from the OperatorHub

[mohitsuman]

@sudhirverma Please refer the screenshot of the welcome page to understand the workflow.

[sudhirverma]

@mohitsuman and @evidolob we already show the welcome page to install the pipeline and I have added the Tekton Trigger button to open the documentation for the trigger.