README.md

GitHub Actions for C++ using CLion

from:

https://zhuanlan.zhihu.com/p/446057486

https://github.com/kirshamir/GitHubActionsExample

参考：

https://docs.github.com/zh/actions/using-workflows

https://www.freedesktop.org/wiki/Software/cppunit/

问题：

GitHub Action 在make时找不到Makefile