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)
Fixed typos based on feedback.

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Merge pull request #7769 from fredlf/1.2.0_release-notes

Adding release notes to docs home