Add milestones subcomand (#149)

issues/pulls show milestones

add mile issues subsubcomand

Add milestones subcomand

Co-authored-by: 6543 <6543@obermui.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/149
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Reviewed-by: Andrew Thornton <art27@cantab.net>

main.go

@@ -44,6 +44,7 @@ func main() {
 		&cmd.CmdTrackedTimes,
 		&cmd.CmdOpen,
 		&cmd.CmdNotifications,
+		&cmd.CmdMilestones,
 	}
 	app.EnableBashCompletion = true
 	err := app.Run(os.Args)