Add "Docker" to Reference pull-down for Command Line

A minor thing, but I noticed that the "Reference" drop-down menu just
says "Command line".  This was fine when we just had one command line,
but now there's also 'Compose command line' and I suspect we may add
others later.  We should qualify the Docker one with the word "Docker"
in front

Signed-off-by: Doug Davis <dug@us.ibm.com>

docs/sources/reference/commandline/cli.md

@@ -2,7 +2,7 @@ page_title: Command Line Interface
 page_description: Docker's CLI command description and usage
 page_keywords: Docker, Docker documentation, CLI, command line
 
-# Command Line
+# Docker Command Line
 
 {{ include "no-remote-sudo.md" }}