Add description of breaking changes and the deprecation cycle to guides.
Add description of breaking changes and the deprecation cycle to guides.

The deprecation cycle can be confusing to contributors. We can add it to
the guide to help contributors.

Inspired by: b4fffc3c68d7be96acd0fc2cc which already added some great
documentation.

Co-authored-by: Adrianna Chang <56e0e0ecf2f5a1ed63a3361922ae89343804687c@shopify.com>

MSP-Greg/rails,yahonda/rails,rails/rails,georgeclaghorn/rails,rails/rails,yahonda/rails,MSP-Greg/rails,yahonda/rails,yahonda/rails,esparta/rails,georgeclaghorn/rails,rails/rails,MSP-Greg/rails,esparta/rails,georgeclaghorn/rails,MSP-Greg/rails,rails/rails,georgeclaghorn/rails,esparta/rails,esparta/rails