The most notable thing here is that we keep the movie iframes running!
So if you're trying different pets for an animated item, the animation
keeps going while the new pet layers load alongside it.
This is also nice for like, the species/color picker form, so we're not
taking away input elements from people who depend on e.g. keyboard
focus.
Not using this on the item page preview yet, but we will!
I like this approach over e.g. a web component specifically for the
sandboxing: while I don't exactly *distrust* JS that we're loading from
Neopets.com, I don't like the idea of *any* part of the site that
executes arbitrary JS unsafely at runtime, even if we theoretically
trust where it theoretically came from. I don't want any failure
upstream to have effects on us!
I copied basically all of the JS from a related project
`impress-media-server` that I had spun up at one point, to investigate
similar embed techniques. Easy peasy drop-in-squeezy!
From an era when we didn't have that! Now we do!
(My motivation is that I'm trying to add new JS to this page and errors
in stickUp are crashing the page early, womp womp!)
