Add .env.default

[kp2pml30]

I think that we should split .env into two files: .env.default which is always loaded and .env that acts as user-defined overrides, loaded afterwards. Because right now when someone adds new .env.example property everyone misses that change and encounters strange errors

[kp2pml30]

that will require patching all load_dotenv into a sequence of such, I can implement it when I have time iff owners agree