Option to read env files from multiple folders.

[D-sense]

I think having an option of passing folder name to Load(folders ...string) or Overload(folders ...string) will help tremendously in loading all env files found. This is extremely beneficial when working with different packages where each package has its own env file within it.

[D-sense]

I submitted a PR for this at #112

[D-sense]

@joho any update on this issue?