fix index_root or app_root not set in .runway-config.json error

[ycrao]

The app_root and index_root values are now located in $config['runway'] .

[ycrao]

ref: https://github.com/flightphp/runway/blob/master/runway#L110-L134

[n0nag0n]

Hey there, thanks for doing this, although I had to do a lot more to it. I needed to still accept the old .runway-config.json file if it was still there and accept the config.php values so it took more refactoring. #673

Thanks for contributing lately! Hop in the discord channel and say hi if you haven't already!