请求支持 [file:read("n")](https://cloudwu.github.io/lua53doc/manual.html#pdf-file:read) luajit的实现在 [lib_io.c](https://github.com/openresty/luajit2/blob/1951d9a4065cb84738d9077c1a77475cc81b4a6d/src/lib_io.c#L207)
