Adds new Docs Style Guide.

Includes changes to mkdocs yml and removes style info from docs Read Me, adding a link instead.

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

Conflicts:
	docs/README.md

Revisions to style guide based on review.

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

More Style Guide revisions based on review.

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

A few more style guide copy edits

Docker-DCO-1.1-Signed-off-by: Fred Lifton <fred.lifton@docker.com> (github: fredlf)
Merge pull request #8500 from fredlf/style-guide

Adds new Docs Style Guide.