Update README.md

Author: jackton1

README.md

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 Precommit hook for [graphql-code-generator](https://github.com/dotansimha/graphql-code-generator) 
 
 
+![Node.js CI](https://github.com/jackton1/graphql-codegen-hook/workflows/Node.js%20CI/badge.svg?event=push)
+
 ## As a pre-commit hook
 
 See [pre-commit](https://github.com/pre-commit/pre-commit) for instructions