描述：匹配指定后缀的文件名
查找：([^\']*)(\.jpg)
替换：img/\0

实例：
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push 'contentimage', 'girl7.jpg'
push '_root'
push 'contentimage', '3lions1.jpg'

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push 'contentimage', 'img/girl7.jpg'
push '_root'
push 'contentimage', 'img/3lions1.jpg'

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