229 enhance config handling

[hackl]

Chang the config to a toml based format. Now the config can be found in pathpyG.toml. This config file can be updated, added and overwritten by a local pathpyG.toml file in the working directory.

toml syntax for the config file can be found here: https://toml.io/en/

NOTE: tomllib is only natively supported by Python 3.11 upwards. Until the python version is changed, a workaround for older versions is implemented based on https://github.com/hukkin/tomli

import sys

if sys.version_info >= (3, 11):
    import tomllib
else:
    import tomli as tomllib

tomllib.loads("['This parses fine with Python 3.6+']")