docs: GitHub Actions CI badge

Signed-off-by: Andy Kenward <4893048+andykenward@users.noreply.github.com>

Author: andykenward

README.md

@@ -1,5 +1,7 @@
 # eslint-plugin-github
 
+[![Node CI](https://github.com/github/eslint-plugin-github/actions/workflows/nodejs.yml/badge.svg)](https://github.com/github/eslint-plugin-github/actions/workflows/nodejs.yml)
+
 ## Installation
 
 ```sh