Fixing issues in command ordering. Adding index.md

Adjust bullets
Entering Seb's comments

Signed-off-by: Mary Anthony <mary@docker.com>

docs/reference/commandline/diff.md

@@ -5,7 +5,6 @@ description = "The diff command description and usage"
 keywords = ["list, changed, files, container"]
 [menu.main]
 parent = "smn_cli"
-weight=1
 +++
 <![end-metadata]-->