docs(format): Tabbed install for operator and halyard

[alexfornuto]

Resolves GitHub issue: #581

This should address the issue raised in #581 by putting the Install instructions for Operator and Halyard into a new set of tabs, so only one method is displayed at a time.

[armory-jenkins]

The title of this Pull Request needs to be changed to match the format:

<type>(<scope>): <subject>

See more details here: https://www.spinnaker.io/community/contributing/submitting/#commit-message-conventions

Some common examples are:

feat(armory.io): add docs.armory.io
fix(parser): grammar and spelling
style(loadingPage): made it super pretty!
refactor(helpMessages): changed order to make more sense

[aimeeu]

Hmmm... I thought this page used an include with armory-operator/op-install-cluster.md... which prompted my comment about limitations of the web framework.

The Armory Operator install steps content is outdated. Can you update to:

You need Kubernetes ClusterRole authority to install the Operator in cluster mode.

You can find the Operator's deployment configuration in spinnaker-operator/deploy/operator/cluster after you download and unpack the archive. You don't need to update any configuration values.

1. Get the latest Operator release:

   Armory Operator

   mkdir -p spinnaker-operator && cd spinnaker-operator
   bash -c 'curl -L https://github.com/armory-io/spinnaker-operator/releases/latest/download/manifests.tgz | tar -xz'

2. Install or update CRDs across the cluster:

   kubectl apply -f deploy/crds/

3. Create the namespace for the Operator:

   In cluster mode, if you want to use a namespace other than spinnaker-operator, you need to edit the namespace in deploy/operator/kustomize/role_binding.yaml.

   kubectl create ns spinnaker-operator

4. Install the Operator:

   kubectl -n spinnaker-operator apply -f deploy/operator/kustomize

5. Verify that the Operator is running:

   kubectl -n spinnaker-operator get pods

   The command returns output similar to the following if the pod for the Operator is running:

   NAMESPACE                             READY         STATUS       RESTARTS      AGE
   spinnaker-operator-7cd659654b-4vktl   2/2           Running      0             6s
   

This whole pages needs review and updating... but that's part of another ticket.