NODE_ENV doesn't work on windows

[yoshuawuyts]

λ npm start

> choo-electon-app-01@1.0.0 start D:\gitwork\choo-electon-app-01
> NODE_ENV=development electron main.js

'NODE_ENV' is not recognized as an internal or external command,
operable program or batch file.

from create-choo-electron, but will also apply here

[ungoldman]

I recommend cross-env as a good cross platform way to set env vars. Alternately we can provide instructions for both platforms.

[yoshuawuyts]

@ungoldman I think cross-env would make sense to use here