[REF] Use pyproject.toml

[jgranley]

Having the package use a pyproject.toml to set up the build, installation, and pip package would be ideal, would modernize the package, and would provide numerous other benefits such as simplified installation, cross platform compatibility, allows pulse2percept to be included in other projects requirements.txt (currently doesn't work because numpy and cython must be installed prior to pulse2percept), and simplified github actions (e.g. wheel build checks).

https://pip.pypa.io/en/stable/reference/build-system/pyproject-toml/