- refact: rename `secrets.py` --> mysecrets.py`
- refact: add more, rename & homogenize dir vars with bash ones.
- FEAT: +`setup.cfg` +`pyproject.toml` to package lib-code.
- feat: add project coordinates in new package(`__init__.py`).
- feat: +`LICENSE.txt` of EUPL v1.2

Rational: refactored as package not to pollute/hide standard-lib modules,
and, through being pip-installable, to facilitate running scripts from dirs anywhere.