Install project module in editable mode

[patrickarmengol]

In order to develop a project using the src layout, the project module should to be installed. Usually this is done with an editable install like: pip install -e . in the virtual environment.

If this is not done, then running something like huak run python -m <mymodule> will fail to find the module. For projects that have scripts configured in pyproject.toml like those initialized with --app, the script is unrecognized when running huak run <mymodulescript>.

See src layout vs flat layout for more info and this snippet in hatch for a reference implementation.

[cnpryer]

Agreed! This is something I've been putting off. Thanks for calling this out.