Pympdata

- fixing version indicators for dependencies in pypi.org-published files (regression introduced when automating package uploads)

- enable CI with Python 3.10
- fix timers documentation (cpu/wall time mismatch)
- JOSS paper updates

added PyPI release automation through GitHub Actions

including JOSS paper draft folder into the main branch

- addressing compatibility with Numba 0.55 (incl. elimination of read-only globals for null arrays)
- refactor around passing arrays & boundary conditions in Stepper (using namedtuple)