This PR adds the ContourPy package, which is a C++ extension that is a dependency
of Matplotlib >= 3.6.0 and Bokeh >= 3.0.0. Note that this is the previous version (1.0.7)
of ContourPy, not the latest one (1.1.0) that uses Meson as I am still trying to get that
to build with the correct compiler flags.
Ian Thomas