Switch to pyproject.toml-based package

[schuenke]

PEP 518 – Specifying Minimum Build System Requirements for Python Projects suggests to use a pyproject.toml file to specify the build dependencies and provide all project-related metadata and Python.org adjusted their Packaging Tutorial accordingly.

PyPulseq currently still uses the "old" concept of a setup.py file, but the ongoing refactoring process (#95, #123) might be the right moment to switch to a ``pyproject.toml` file.

The advantage of a pyproject.toml file is that it can also be used as config file for almost all current linters and formatters. A simple example of a pyproject.toml file including some additional tool configurations can be found in the pyproject-toml-cheat-sheet Github Repo.

What are your opinions?

[sravan953]

Let's do it. I think this should be in a dedicated branch before merging into dev, and then main.

[schuenke]

Changed with #195 already