docs: clarify building of adapter-node (#8881)

* Update 40-adapter-node.md

It wasn't clear to me that `npm run build` was needed

* Update 40-adapter-node.md

---------

Co-authored-by: Rich Harris <[email protected]>

Author: gregorybleiker

documentation/docs/25-build-and-deploy/40-adapter-node.md

@@ -22,7 +22,9 @@ export default {
 
 ## Deploying
 
-You will need the output directory (`build` by default), the project's `package.json`, and the production dependencies in `node_modules` to run the application. Production dependencies can be generated with `npm ci --prod` (you can skip this step if your app doesn't have any dependencies). You can then start your app with this command:
+First, build your app with `npm run build`. This will create the production server in the output directory specified in the adapter options, defaulting to `build`.
+
+You will need the output directory, the project's `package.json`, and the production dependencies in `node_modules` to run the application. Production dependencies can be generated with `npm ci --prod` (you can skip this step if your app doesn't have any dependencies). You can then start your app with this command:
 
 ```bash
 node build
@@ -191,4 +193,4 @@ function shutdownGracefully() {
 
 process.on('SIGINT', shutdownGracefully);
 process.on('SIGTERM', shutdownGracefully);
-```
+```