tweak readme (#3591)

Author: Rich-Harris

.changeset/thin-swans-cheat.md

@@ -0,0 +1,5 @@
+---
+'create-svelte': patch
+---
+
+Tweak README

packages/create-svelte/shared/README.md

@@ -29,10 +29,12 @@ npm run dev -- --open
 
 ## Building
 
-Before creating a production version of your app, install an [adapter](https://kit.svelte.dev/docs#adapters) for your target environment. Then:
+To create a production version of your app:
 
 ```bash
 npm run build
 ```
 
-> You can preview the built app with `npm run preview`, regardless of whether you installed an adapter. This should _not_ be used to serve your app in production.
+You can preview the production build with `npm run preview`
+
+> To deploy your app, you may need to install an [adapter](https://kit.svelte.dev/docs#adapters) for your target environment.