Issues with installation

[srmnitc]

The installation of atomistics package in a clean env caused the following issues:

• phonopy is not automatically installed
• structuretoolkit is not installed; and try except block prevents error from being captured

[jan-janssen]

Yes, both are optional dependencies of the atomistics package:
https://github.com/pyiron/atomistics/blob/main/pyproject.toml#L41

I guess we should update the error message to advise users to install the optional dependencies. @srmnitc Can you open a pull request?