Add Python3 to the list of build dependencies

[carlo-bramini]

README.md lists several build dependencies (boost, libpng, etc...).
Perhaps, Python3 needs to be added to this list.

[stohrendorf]

Indeed, thanks for the hint.

[carlo-bramini]

Indeed, thanks for the hint.

I'm wondering if you could update the build instruction with Python and vcpkg, because I'm trying to compile with MSVC and after some tests I'm still getting "Python 3 Library not found" from CMake. Installing also the official 3.10.7 binaries of python and adding the tool to the path didn't solve the trouble.
Thank you.

[stohrendorf]

That will be part of the instructions. In your case, what you need is something like -DPython3_ROOT=E:\Python38 when calling cmake.