fix: Adds a new section on building the app for production.

README.md

@@ -57,6 +57,19 @@ cp .env.sample .env
 
 This app does not enforce any authentication, **do not put this app on the internet**.
 
+### Building
+
+The app contains two moving parts as described in [Project setup](#project-setup): the user facing React app and the server. These two needs to be built separately. To produce JavaScript files that can be run with plain `node` you can run the follwing two scrips defined in `package.json`.
+
+- `pnpm build:remix` Builds the React app and puts the final output in `./build`.
+- `pnpm build:server` Builds the server and puts it in `./build-server`. This step depends on the `pnpm build:remix` step.
+
+After successfully running the commands above the app can be started with
+
+```shell
+node ./build-server/server.js
+```
+
 ### App container
 
 Every running environment is different, but to help getting this app deployed `./example.Dockerfile` will produce an image that runs the app.