Blocks fails to load reliably on slow networks

In a school setting with a less than ideal network, it very often takes students several reload attempts before code.world/blocks will load for them. Not sure if this is some kind of race condition, or just a consequence of the size of the generated JavaScript in the `funblocks-client` package.

Whatever the case, this is a serious problem. It not only takes 5 to 10 minutes away from each class session, but far worse, it leaves students feeling like can't use the site without adults there ready to handle the problems.