Allow the loading from Environmental variables

[lyz-code]

Hi @dbatten5 long time no see, hope everything's fine on your end.

@marcules has implemented in this pr a way to override the configuration with environmental variables, in case you are interested in adopting it in maison.

If you're not, feel free to close it, I just wanted to avoid you work duplication.

Take care

[dbatten5]

Hey, yeah that's a nice feature. I'm a bit stretched at the moment but maybe I can include this when I have a moment, will close for the meanwhile and hopefully I can come back to it soon