Use pyproject.toml, hatch, importlib, black, cookiecutter prompts

[rly]

Fix #70

Also apply additional improvements in code style and quality (black, ruff, codespell), use more human-readable cookiecutter prompts, use importlib and pathlib, and importantly, remove the step where the spec files were copied into src/pynwb/package/spec/ after running pip install . locally, which was very confusing for folks and easily led to errors -- see https://github.com/catalystneuro/ndx-photometry/pull/6#issuecomment-1583072813