[exercise] Create a postmortem template

[tylerauerbeck]

📝 Description

The way that a postmortem is run can directly impact the information that is shared there and the resulting actions that are taken. To ensure that one is run smoothly, it can be beneficial to have a template that helps you focus in on what you are trying to achieve. In this exercise, we'll look to build our template and highlight the key areas that are important to a general postmortem

✅ A/Cs

• Create building blocks that can be used to put together a postmortem template
• Identify if there are existing templates in use by other groups at RH (ideally) or other good examples from others out in the wild that we can link to / reference.

Related to #10