MHD slow-moving shock fix #1367
Description
Describe the proposal
Implement the MHD slow-moving shock fix from Lee (2011): https://ui.adsabs.harvard.edu/abs/2011ASPC..444..236L/abstract
Describe alternatives you've considered
A clear and concise description of any alternative solutions you've considered.
Additional context
https://flash.rochester.edu/site/flashcode/user_support/flash_ug_devel/node192.html#SECTION010121100000000000000