Adding release notes to docs home

This is a temporary solution until we have a dedicated release notes page with automated content.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)

(cherry picked from commit 1c3b732f8a6ed6f1d01a6ecacc6753899842c2f0)
Fixed typos based on feedback.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)

(cherry picked from commit 810c231b912c0a12acb8eb82a3756276e47fa632)
Merge pull request #7803 from docker/post-1.2.0-docs_update-2

Post 1.2.0 docs update 2