py::overload_cast missing py::const_

[genyez]

A separate issue from https://github.com/troldal/OpenXLSX/issues/243

Let's see Python/library/pyXLCell.cpp around line 69

def("offset", py::overload_cast<uint32_t, uint16_t>(&XLCell::offset), ....

I encountered a link error( or compile? not sure), said signature not matched, which I've fixed by adding a py::const_, making it like: py::overload_cast<uint16_t, uint16_t>(&XLCell::offset, py::const_)

There were many of that like XLWorksheet::cell, &XLWorksheet::range, etc.

Were those correct fixings? Or there was some misunderstanding or misconfigurations?

In addition, I found this bug back in Apr 30th. Just close it if it has been fixed, appreciate it!