Publish `plinder` on PyPI for easier installation

[padix-key]

This PR adds a CI step that publishes the package on PyPI and adopts the docs accordingly.

[github-actions[bot]]

Coverage report

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File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
src/plinder/core/utils
config.py
src/plinder/data
smallmolecules.py
src/plinder/eval
__init__.py
src/plinder/eval/docking
stratify_test_set.py
write_scores.py
Project Total

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