Use config.json instead of config.js

[arunoda]

With config.js we usually load modules. It'll be great, if we can do this with a simple .json file.

We could also support pattern based file loading.
This will simplify things.

If the user needs, he could use import a .js file of his own and do any custom JS stuff as well.

[ndelangen]

json is a pretty poor format for manual configuration in my humble opinion:

• no comments
• no variables
• freaking qoutes everywhere
• no trailing comma's allowed

I think we're doing everyone a favour by not having them deal with that 🤗