Trim whitespace for strings

[DeanPDX]

Karl on the go forum brought up that it would be nice if we automatically trimmed whitespace on strings:

I just found an issue in dotconfig. It’s simple, can you make sure that strings are trimmed? A simple strings.TrimSpace() will do. Otherwise there could maybe be an error in some cases. (I do not believe that someone intentionnaly has a .env value with a leading or trailing space, do you?

I originally thought about trimming whitespace but I wasn't sure if there was any valid use case where somebody might want whitespace. If that is the case, we could support it with an option.