Document: Ensure Critical alerts have complete playbook entries

Provide copy/paste commands to issue

easy to follow checks/next steps (think needing to wake up in the middle of the night to resolve)

Current upstream doc is here: https://github.com/openshift/elasticsearch-operator/blob/master/docs/alerts.md 

(Currently we are focusing on Critical in this task to make this more bite-sized – we will have follow up for warning and info as well)

Acceptance Criteria:

• Ensure that any alerts that are marked as critical have proper diagnostic steps and action steps so that an user can resolve the alert
• Possibly also ensure that our alerts are using the run{{book_url}} variable to point to our playbook location (tbd if this will be upstream or downstream)