Pymatching

Adds support for creating Matching objects from [retworkx](https://pypi.org/project/retworkx/) graphs

Improves the error message for parallel edges.

* Adds support for negative edge weights
* Fixes an issue with Python 3.10 Windows builds

* Allow array inputs for `timelike_weights` and `measurement_error_probabilities` (separate values can be supplied for each check in the check matrix)
* Rename `measurement_error_probability` to `measurement_error_probabilities` (but maintaining backward compatibility)
* Rename edge attribute `qubit_id` to `fault_ids` (but maintaining backward compatibility - `qubit_id` still accepted)

- Matching graphs with multiple connected components are now supported
- `pymatching.Matching.add_edge` method added to allow `pymatching.Matching` graphs to be constructed incrementally (rather than just via NetworkX graphs or scipy/numpy check matrices)
- It is now permitted to include only a subset of the qubit_ids from 0...(num_qubits-1) as edge attributes.
- Added `num_nodes`, `num_edges` and `num_detectors` properties to `pymatching.Matching`, and `pymatching.Matching.stabiliser_graph` renamed to `pymatching.Matching.matching_graph`
- Doctest examples added to docstrings
- Python type hints added
- Various changes to the C++ code and pybind11 bindings (e.g. refactoring, renaming and addition of docstrings and doctest examples), so that these can be more easily used directly by the user if desired (rather than just via the main `pymatching.Matching` class)

- Fixes bug that could cause the Python interpreter to crash
- Default `num_neighbours` changed from 20 to 30