[PROPOSAL] migrate to pyproject.toml for packaging

[SauravMaheshkar]

pyproject.toml is the new standard for packaging python packages, setup.py is now deprecated (first introduced in PEP 518 and later expanded in PEP 517, PEP 621 and PEP 660). This PR proposes to switch from the legacy setup.py method in favour of pyproject.toml. This would lead to a overall better project structure because all requirements would be managed within a single pyproject.toml file instead of 5 separate text files. It also allows for dynamic version allocation (reads automatically from /__init__.py).

I'd like to raise the discussion about shifting to a newer modern build backend.

A lot of repositories have shifted to pyproject.toml such as PyTorch Geometric, Geoopt and Flax !

More than happy to work on this issue