use 'img' instead of docker  #43

Hi Wei,

Thank you so much for developing this action, it's a very useful action 💯 . I have some problems with using docker. We are using 'img' for building docker images. My question is :

1. is it possible to use 'img' instead of docker
2. Is there any possible copy particular folder instead of the full repo

Kind Regards,
Sathish