Performance issues on low-spec devices

[galacticglum]

Web app feels sluggish on low-spec devices that I've tested (e.g. MacBook Air 13-inch 2017). We might want to slim down the app (by default) on devices that are lower spec, or look into how we can optimize rendering.

• [ ] #56

[eamonma]

I think we can do some optimization with the schedule renderer, since that's in a context with everything, every time the schedule updates essentially the whole app rerenders.