Editing the root html file doesn't hot reload

[adam-lynch]

Creating a new issue for this so it can be tracked, originally discussed in #751.

[LinusBorg]

thanks. We will shortly be switching to webpack-dev-server (#975), so we should revisit this issue after that.

Because the config we had to comment out as explained in #751 isn't even available anymore after that switch. So we have to see how that reload functionality can be re-introduced (or maybe it just works, I haven't tested that specifically with the new setup yet).