README for vercel deployment of demo app (#639)

examples/svelte-kit-demo/README.md

@@ -1,5 +1,11 @@
 # svelte-kit-demo
 
-Place to try out [@sveltejs/app](https://github.com/sveltejs/kit). Very basic and incomplete, many things haven't yet been thought through.
+This is a simple app to demonstrate a few different features of SvelteKit, and to ensure that the various adapters are working correctly.
 
-To start the app in development mode do `npm run dev`. To build, use `npm run build`. This will use whichever adapter is specified in `svelte.config.cjs`, which will also need to be installed (or linked).
+## Deployments
+
+### Vercel
+
+- URL: https://kit-zeta.vercel.app/
+- Info: https://vercel.com/sveltejs/kit
+- Build command: `npm run build:vercel`