Add description to pyproject.toml

[kevin-paulson-mindbridge-ai]

Adding a description to pyproject.toml will display this package nicer on the Python Package Index (PyPI) and listing tools like poetry show.

I suggest "Provides the core functionality for pydantic validation and serialization" based on the readme.

[kevin-paulson-mindbridge-ai]

Or maybe there is a description somewhere else but it's not being applied:

compared to:

[kevin-paulson-mindbridge-ai]

Looks like this was resolved by #1214