Add a section for installing Tekton Pipelines on OpenShift

[tomgeorge]

Changes

Add a section for installing Tekton Pipelines on OpenShift

Outlines how to add the anyuid scc to the tekton-pipelines-controller SA in order to successfully get the webhook pod to start.

Clarifies #609

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[tomgeorge]

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[vdemeester]

👍

[vdemeester]

Actually we may want to move ### Installing Tekton Pipelines on OpenShift just before ## Configuring Tekton Pipelines (:angel: so that You are now ready to … is not under the Openshift heading)

[vdemeester]

/ok-to-test

[hrishin]

These commands requires admin privileges, is it better to add a note?
Or
Shall we add oc login as admin instruction as the first step?

[sthaha]

we also need the hack cluster-admin priv oc adm policy add-cluster-role-to-user cluster-admin -z tekton-pipelines-controller -n tekton-pipelines , don't we?

[tomgeorge]

In my testing, I only needed anyuid for the tekton-pipelines-controller sa.

[tomgeorge]

/test pull-tekton-pipeline-integration-tests

[vdemeester]

/lgtm

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: tomgeorge, vdemeester

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[vdemeester]

/test pull-tekton-pipeline-integration-tests