PyMatching v0.4.0

• 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)