inconsisting case handling across different OS

[kmomberg]

I added lowercase vars into .env file, and they were handled fine in Windows, but not in Linux. In Linux seems to be a requirement that all vars are uppercase.

Not sure if this is a bug, or just something that needs to be stated in the README (like "all env vars needs to be uppercase").

[yaroslav-gwit]

It's a UNIX convention to set all your VARs to uppercase, but it doesn't explain why the lowercase variables don't work in godotenv.