Update readme

Author: hugoalh

README.md

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 # GitHub Actions Toolkit (PowerShell)
 
 [⚖️ MIT](./LICENSE.md)
+[![CodeFactor Grade](https://img.shields.io/codefactor/grade/github/hugoalh-studio/ghactions-toolkit-powershell?label=Grade&logo=codefactor&logoColor=ffffff&style=flat-square "CodeFactor Grade")](https://www.codefactor.io/repository/github/hugoalh-studio/ghactions-toolkit-powershell)
 
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