Attention and layers for injecting sparse data

What’s Changed

• Adding pyproject.toml, minimal setup.py, removed requirements.txt by @bnb32 in #57
• Bnb/sup3r_concat_obs by @bnb32 in #61
• Bnb/sup3r embedder by @bnb32 in #62
• Update publish_to_pypi.yml by @bnb32 in #63

Full Changelog: v0.0.30...v0.0.31