message: chore: add github action badge
diff: <a href="https://travis-ci.org/remaxjs/remax">
  <img src="https://img.shields.io/travis/remaxjs/remax/master?style=flat-square" alt="Travis CI build status" />
  </a>
  + <a href="https://github.com/remaxjs/remax/actions?workflow=Node+CI">
  + <img src="https://github.com/remaxjs/remax/workflows/Node%20CI/badge.svg" alt="CI build status" />
  + </a>
  <a href="https://codecov.io/gh/remaxjs/remax">
  <img src="https://img.shields.io/codecov/c/github/remaxjs/remax/master.svg?style=flat-square" alt="Codecov" />
  </a>
  