add shell script version of README.md

as GitHub user @v3aqb says:
"github hosts source code, not newsletter. stop the abuse." at
https://github.com/greatfire/wiki/issues/1#issuecomment-30562356

let's add some code to this fabulous project!

This is the initial shell script version of "免翻墙镜像" project, it simply
ask a cat to read the README.md file to stdout.

Signed-off-by: Ｖ字龍(Vdragon) <pika1021@gmail.com>