Add Openshift/OLM specific installation instructions

[trgeiger]

What is the URL of the document?

Which section(s) is the issue in?

I think this needs to be determined. My impulse is to add the instructions as a section under Tutorials like the machine learning example, but I could see it existing under Getting Started I guess, or a new section entirely.

What needs fixing?

Adding documentation and determining the appropriate section for the new docs.

Additional context

This will be documenting the extra steps needed to set up ACK operators in an Openshift cluster using OLM, i.e. running code-generator to create OLM-specific bundles, installing the operators into Openshift, and setting up single- or multi-tenant configurations. It will also eventually have information on the presence or absence of the AdoptedResource CRD, once we merge some changes to how the AdoptedResource reconciler is handled for OLM installations (see aws-controllers-k8s/runtime#59)

[acornett21]

These new docs can be their own OpenShift subheading, that way they can live on their own persay.