GitHub Actions to lint Nim code

[jiro4989]

I wrote a GitHub Actions to lint Nim code.  
nimlint-action is inspired by 
[reviewdog/action-eslint](https://github.com/reviewdog/action-eslint).  


[https://github.com/jiro4989/nimlint-action](https://github.com/jiro4989/nimlint-action)

This action notices compile message to Pull Request.

Examples.
    
    
    import strutils
    
    echo "hello world"
    
    Run

Nim prints **Warning:** if you compile this code.
    
    
    /tmp/main.nim(1, 8) Warning: imported and not used: 'strutils' 
[UnusedImport]
    
    Run

This action notices these message ( **Hint:** , **Warning:** , **Error:** ) to 
Pull Request.