Swap into using pyproject.toml and setup.cfg

[gnikit]

• [x] Moves the build from setup.py to setup.cfg and pyproject.toml, since setup.py will soon be deprecated.
• [x] Uses setuptools_scm for automatic version incrementation. Can be inferred from git and GitHub Releases
• [x] Updaes instructions on how to install
• [x] Drops Python 3.5 support, has reached EOL and setuptools_scm does not support it.

Fixes #132 Depends on #131 for README formatting

[gnikit]

@awvwgk do we need both conda and pypi test workflows? Because the conda-forge feedstock draws from GitHub I think we should only unittest PyPi from 3.6-3.11-dev

[awvwgk]

do we need both conda and pypi test workflows? Because the conda-forge feedstock draws from GitHub I think we should only unittest PyPi from 3.6-3.11-dev

I don't see much difference between testing against the Ubuntu packaged Python and the conda-forge packaged Python. The Python version range is open to discuss, we have a pure Python package, so there shouldn't be much surprises, but of course we might have to support even Python versions which reached EOL like Python 3.5 and 3.6. Not sure about testing development Python version.

[gnikit]

@awvwgk same here, ready to merge