Add a modern version of `pyproject.toml` to plugins

[blythed]

Currently this is written to __init__.py. The modern approach is in pyproject.toml as in the main project:

[project]
name = "superduper-framework"
description = "🔮 Bring AI to your favourite database 🔮"
readme = "README.md"
version = '0.5.0.dev'