Add warning about OpenZGY/Python not being actively maintained. Use the Python wrapper around OpenZGY/C++ if possible.
Set up build rules for Valgrind (memory checker) and LCOV (coverage tool)
Freeze the version of Python matplotlib at < 3.4 because a new version has been published that only supports Python 3.7 or later, and several major distros (e.g. CentOS 8) are still on 3.6.