implement scandeps module to detect dependencies of a project

[amol-]

This introduces a self contained scandeps.py module that is designed to detect dependencies of Python projects.
Combined with picopip.py it provides a full set of utilities to find dependencies of a project based on its environment or based on the project code itself.

This can be used like

>>> scandeps.scan_project("./project")
["pandas", "requests"]

It has support for

• Python code (.py)
• Jupyter Notebooks (.ipynb)
• Quarto documents (.qmd)