Ecriture-shopify

- add import of `shopify_to_ec` in __init__.py
- correction changelog url in `pyproject.toml`

- correct python = ">3.9"
- remove "json with comments"

- support of python 3.9 and higher (following Pandas 2.1.0)
- tox integration for pytest
- changelog added
- minor modifs (flake8 precision, gitignore adaptation, etc)

- Adding compability with python 3.8, 3.9 and 3.10.
- New added tests for tools.read_config module

- Patch to correctly import ecriture-shopify in GHA workflow.

- First official release.