Adjust Vite HMR implementation

[jods4]

server.reloadModule(mod) is documented as the way to push HMR here: https://vitejs.dev/guide/api-javascript.html#vitedevserver
I've used it in beforeWriteFiles and it worked for me.

I made updateRoutes non-async because:

• You could await reloadModule but I don't think you should, and you didn't await the websocket in previous code either
• Everywhere you call updateRoutes, you don't await it.
• Interface ServerContext says it returns void not Promise.

[posva]

Thanks, I will have to give it a try. In the end there were other parts that were crucial during HMR like data loaders. I wish it was easier to write unit tests for HMR, it would allow me to make changes more confidently.