This changes the default value of `dotenv-load` from `true` to `false`. This
is a backwards incompatible change, and will require a minor version bump.
If a `.env` file is found and loaded, but the `dotenv-load` setting hasn't been explicitly
set to true, print a warning to stderr. In approximately six months, `dotenv-load` will
change from defaulting to true to defaulting to false, which will be a potentially breaking
change in behavior for justfiles which elicit this warning.
See this issue for more details:
https://github.com/casey/just/issues/469
