Created by: joelhawksley
This PR introduces a Lifecycle page to the design guidelines on primer.style.
Context
As part of our goals we're working on increasing the maturity of Primer, to make it more robust and consistent, and to create clarity for people working with the system. Our component libraries have diverged as we experimented and developed different parts of Primer, and we don't have all the pattern coverage we think consumers need across the system. These criteria are meant to establish baseline expectations for components in Primer as they mature over time.
Notes
We had originally titled these levels maturity statuses but I feel that the term Lifecycle better captures the intention for this to be a process that we move components through. I also used the term milestone in place of status for similar reasons.