Fill .snekrc.example

[Martmists-GH]

Having an example .snekrc with all possible values filled would be great to have. Since this file will be massive, I'm assigning all of us to work on it.

Check the code and the respective linter's sections to see what values have to be filled in what way.

[AraHaan]

I personally think we should do rst docs for this all and then also provide an example there to make it all easier.