added mac runner to CI

[shimwell]

Description

What do people think should we enlarge the CI suite to include different operating systems such as Mac OS. Currently we run the CI on ubuntu-22.04 only. I've noticed a few PRs aimed at improving the Mac experience and recently I've been testing GEOUNED with OpenMC on a Mac in the CI. The Ubuntu runner worked and the Mac runner came back with a error. Which go me thinking should we enlarge the openmc CI to include Mac OS
Fixes # (issue)

Checklist

• I have performed a self-review of my own code
• I have run clang-format (version 15) on any C++ source files (if applicable)
• I have followed the style guidelines for Python source files (if applicable)
• I have made corresponding changes to the documentation (if applicable)
• I have added tests that prove my fix is effective or that my feature works (if applicable)