Help for writing an app (running zones using Karvonnen method)

I just saw the PR come in: https://github.com/espruino/BangleApps/pull/2591

I've got to say, I'm a little anxious about adding this to the default run app - I remember folks with Bangle.js 1 complaining that even the current app could run into RAM issues with some extra widgets installed - this would make it almost unusable?

The whole idea of me spending a bunch of time creating the exstats library was to try and make it easy for others to create new run apps with minimal code duplication, and to keep the standard run app as a very simple base that others could learn and build from.

While the Karvonnen stuff looks great, it more than doubles the code size of the run app (145 to ~400 lines?)

Maybe we should instead just rename it as a brand new app run-karvonnen or something?