Add support for 4 space indentation when writing the package.json

[peterdemartini]

Currently, our project uses 4 space indentation, and when I use this tool it will change the package.json to use 2 spaces, making more changes than it needs to.

It would be nice if syncpack could detect the indentation, like npm and yarn.

[JamieMason]

Thanks @peterdemartini, should be easy enough 🤞 I should be honest and admit though that this will be a lower priority issue but I'm happy for it to go in sure.