update README.md

sample/workdir/monster.json

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+{"name":"monster","root":{"id":1,"name":"Sequence","desc":"怪物测试AI","args":{},"children":[{"id":2,"name":"Sequence","desc":"攻击","args":{},"children":[{"id":3,"name":"GetHp","args":{},"output":["hp"]},{"id":4,"name":"Cmp","args":{"gt":50},"input":["hp"]},{"id":5,"name":"Log","desc":"攻击","args":{"str":"Attack!"}}]},{"id":6,"name":"Log","desc":"逃跑","args":{"str":"Run!"}}]},"desc":"怪物测试AI"}