Unable to generate zh_TW locale of site document

Here is my code: https://github.com/doggy8088/mybatis-3/tree/patch-1

I tried to run mvn clean site on my project. I expected to generate zh_TW and zh_CN site in the target/site folder. But it didn't generate it. Only target/site/zh been generated which means the Apache Maven Site Plugin unable to distinguish between zh_TW and zh_CN locale.

I checked the source code in the src\main\java\org\apache\maven\plugins\site\render\AbstractSiteRenderingMojo.java file. This only read locale.getLanguage() and it just ignored the Country or Region part of the locale totally.

I think it's bug.