Decaylanguage

* Dependencies:
- Dropped Python 2 (2.7) support.
- Added support for Python 3.10 and dropped 3.5.
- Dependency on `lark-parser` upgraded to recent versions.
* Tests:
- Dependency on Pytest upgraded.
- Added new pre-commit hooks and updated various versions of existing hooks.
* Miscellaneous:
- Added Nox support.

* Dependencies:
- Package dependent on ``Particle`` version 0.16.
- Support for Python 3.5 removed.
* Universal representation of decay chains:
- Documentation updates.
* Tests:
- CI enhanced adding isort checks to pre-commit hooks.
- Various hooks version updates.

* CI and tests:
- Run the CI on Linux, MacOS and Windows.
- Re-added coverage tests replacing Coveralls with Codecov.
- Removed Azure pipelines since superseded by GitHub Actions.

* Parsing of decay files (aka .dec files):
- Fix to parsing of a couple of decay models (subtletly of Lark parsing priorities).
* Miscellaneous:
- CI updates.

* Universal representation of decay chains:
- ``DecFileParser.print_decay_modes()`` enhanced.
- Fix to visualisation of ``DecayChainViewer`` instances in notebooks.
* Miscellaneous:
- CI improvements and updates.

* Notebook clean-ups and improvement to ``environment.yml``.