doc: mention apm help <command>
doc: mention apm help <command>

bcoe/apm,VandeurenGlenn/apm,pusateri/apm,bcoe/apm,gutsy/apm,fscherwi/apm,VandeurenGlenn/apm,bcoe/apm,Nikpolik/apm,ethanp/apm,pusateri/apm,AtaraxiaEta/apm,jlord/apm,atom/apm,jlord/apm,AtaraxiaEta/apm,pusateri/apm,bcoe/apm,AtaraxiaEta/apm,bcoe/apm,atom/apm,bcoe/apm,AtaraxiaEta/apm,ethanp/apm,pusateri/apm,Nikpolik/apm,ethanp/apm,fscherwi/apm,VandeurenGlenn/apm,jlord/apm,pusateri/apm,fscherwi/apm,VandeurenGlenn/apm,ethanp/apm,bronson/apm,fscherwi/apm,VandeurenGlenn/apm,AtaraxiaEta/apm,gutsy/apm,AtaraxiaEta/apm,gutsy/apm,jlord/apm,pusateri/apm,Nikpolik/apm,VandeurenGlenn/apm,fscherwi/apm,ethanp/apm,bronson/apm,atom/apm,jlord/apm,fscherwi/apm,atom/apm,gutsy/apm,jlord/apm,bronson/apm,bronson/apm,ethanp/apm,Nikpolik/apm