How does this work when webpack-dev-server doesn't output anything on the file system?

As far as I can tell, this injects the websocket code that talks to webpack-dev-server into each entry, so that they can be notified that webpack-dev-server has rebuilt and trigger a reload in the browser. But webpack-dev-server doesn't seem to output anything like normal, it just keeps everything in memory, so I'm not able to load the html files, e.g. inside a Chrome Extension. webpack-dev-server seems to be limited to only load things from its built in web server?

Start by reproducing the plugin with webpack-dev-server and a Chrome Extension entry, then inspect how the websocket reload code is injected into entries. Confirm whether the requested outcome is filesystem-accessible output or another loading path, and define done as a documented or working way to load the generated HTML outside webpack-dev-server.