fix(deps): fix package exports, default must be last

[rdy]

When using dotenv-mono under webpack (target: node), it throws an error when the package is loaded because "default" isn't the last entry in package.json.

According to the documentation in node, the order of this actually matters, so this PR is to avoid the error from webpack. This is also detailed in webpack documentation.

[marcocesarato]

Thanks for your pull request! I've merged it in and released the change. Appreciate your contribution to fixing that webpack issue with dotenv-mono. Thank you so much!