[Suggestion] Move `numpy` to optional dependencies.

[XzzX]

Since python-workflow-definition restricts to numpy<2 it is complicated to depend on this repo to get the pydantic pwd specs.

[jan-janssen]

I did a test with the latest version of the different workflow frameworks and it seems aiida-workgraph still requires numpy<2 but this does not affect the Python Workflow Definition, so I removed the restriction in #148

[jan-janssen]

Does this resolve your issue?

[XzzX]

I hope so. Can you do a 0.1.2 release so I can depend on it? Thx.

[jan-janssen]

It took a little longer, but the new version is now available on pipy and conda.