dotenv should look up in parent directories for .env

My .env file is at the root of my project, but when running tests, the current working directory is within test modules.

This would match the behavior of https://github.com/dotenv-rs/dotenv/tree/3c1a77bc95821777e5ceb996c5e0b082f2a3ea38#usage and https://github.com/theskumar/python-dotenv.