Conversion between std::chrono and numpy.datetime64

[phil-zxx]

Using #include <pybind11/chrono.h> we can define

def(py::init([](const std::chrono::system_clock::time_point& obj)

so that we can convert between std::chrono and python's datetime.

Is there a similar concept for conversions between std::chrono and numpy's datetime64? I had a look at pybind11/numpy.h but couldn't find anything.

I am happy implement it and submit a PR, if someone could point me in the right direction for how to do it. Many thanks!

[phil-zxx]

I've tried it myself, please see PR.