------------------
* Add `vf cdproject` command to switch to the project directory matching the name of the currently activated virtual environment
* Add `vf togglepackages`, as `toggleglobalsitepackages`, which will enable or disable the visibility of packages installed outside the virtual environment
* Add `VIRTUALFISH_DEFAULT_PYTHON` environment variable to use the specified Python executable as the default Python interpreter to use when creating a new virtual environment
* If set, deactivate `PIP_USER` when a virtual environment is active