Tatsu

- Fix that settings passed to `Context.parse()` were ignored. Add `Context.active_config` for the configuration active during a parse
- Define `Node._parent` as part of the `dataclass`

- Make `AST` and `Node` hashable. Necessary for caching `Node.children()`
- Implement `Node.__eq__()` in terms of identity or `Node.ast.__eq__()__`
- Fix regression in which rule order is lost in generated parsers ([dtrckd](https://github.com/dtrckd))
- Restore `Node.ast` (was removed because of problems with `__eq__()`)
- Get `Node.children()` from `Node.ast` when there are no attributes defined for the `Node`. This restores the desired behavior while developing a parse model.

* Now ``config: ParserConfig`` is used in ``__init__()`` and ``parse()`` methods of ``contexts.ParseContext``, ``grammars.Grammar``, and elsewhere to avoid the very long parameter lists that abounded. ``ParseContext`` also provides clean and clear ways of overridinga group of settings with another
* All names defined in the successful choice in a rule are now defined in the resulting `AST`_. Names within optionals that did not match will have their values set to ``None``, and closures that did not match will be set to ``[]`
* Moved build configuration from ``setup.py`` in favor of ``setup.cfg`` and ``pyproject.toml`` (`KOLANICH`_)
* ``Node.children()`` is now computed only when required, and cached
* Classes in generated object models are now ``dataclass``
* Optimize and get rid of bugs and annoyances while keeping backwards compatibility
* Drop support for Python < 3.10

* Fix bug in which rule fields were forced on empty ``AST`` (Victorious3)

* Several important refactorings in ``contexts.ParseContext``
* Make ``ignorecase`` settings apply to defined ``keywords``
* Move checking of keywords used as names into ``ParseContext``
* Output of generated parsers again matches that of model parsers
* Improve *"expecting one of:"* messages so elements are in declaration order
* Stop code generation if there are closures over possibly empty expressions
* Preserve name declaration order in returned ``AST``
* Update the bootstrap parser (``tatsu/bootstrap.py``) to the generated parser
* Now generated parser's ``main()`` only outputs the JSON for the parse ``AST``
* Minor version bumped in case the many fixes break backwards-compatibility
* Minor documentation issues fixed
* All tests run with Python 3.8, 3.9, 3.10

* 156 Clarify limitations of left-recursion in PEG (apalala).
* 159 Clean up examples and tutorial, upgrade them to Python 3 (okomarov).
* Test with Python 3.9 (apalala)
* Update CircleCI build (apalala)