Essentially, I took the code from the MUDKIP_Mud2 package and reworked it. After a lot of "issues" (some of which were simply me), I seem to have it in a good working condition.
mupdate is on GitHub and includes both the script itself and another script that can be used as a drop-in script.
The drop-in script is called Updater.lua and it will automatically download mupdate from the latest release and run it on every execution. It is setup for muddler through the use of __PKGNAME__, however, you can put it in your package and just replace all instances with your own package name, or name it something else entirely.
Definitely a shout out to 11BelowStudio (Parasocial Catgirl on Mudlet's Discord) for the MUDKIP_Mud2 package from which I so lovingly, and liberally, pilfered