Improve reprodicibiity and reduce bugginess of additional animated subplot code

[Bergam0t]

Adding additional subplots and animating them is definitely a hacky workaround at best.

It's now functioning correctly in the HEP project example, but ensuring all traces were visible both at the start and for the duration, not duplicated once the animation began, and animated correctly, was tedious and didn't always seem to behave in a logical manner.

I think further investigation needs to be done into how the frames are structured directly after coming out of the initial plotly express call and try to tie that in better to the setup of the additional traces and the final passing of the traces list.

I don't think there's an easier way to set this up either without completely rewriting the initial animation call (which is possible, but a bit of a faff) to return a trace instead of a figure, which could then be added to a subplot. The play bar etc. would then have to be set up in a more manual way. Not insurmountable but I think the current approach - plus detailed documentation on how to extend this with additional subplots - is going to be the most flexible and lowest-maintenance approach.