常用命令功能

xlings version: pre-v0.0.1

Usage: $ xlings [command] [target]

Commands:
	 run,      	 easy to run target - sourcecode file
	 install,  	 install software/env(target)
	 drepo,    	 print drepo info or download drepo(target)
	 update,   	 update xlings to the latest version
	 uninstall,	 uninstall xlings
	 help,     	 help info

Project Commands: (need config.xlings)
	 init,     	 init project by config.xlings
	 book,     	 open project's book in default browser
	 checker,  	 start project's auto-exercises from target

repo: https://github.com/d2learn/xlings