Optional cache busting and bundlers

[kamranayub]

Also mildly annoying is that some implementations of Loadable add a cache busting URL parameter by default whereas others don't, and the bustCache field became private at some point. This seems like the worst possible implementation, I assume it is an oversight :-). For my case, I use a webpack plugin that adds a hash to the filename, so I don't need a cache busting URL parameter, so I did a little hack to disable it by setting the private _bustCache field where it exists here: https://github.com/dcgw/super-metronome-hero/blob/main/resources.ts#L93-L98

Originally posted by @djcsdy in #2522 (reply in thread)