Add preprocess to the adapter-static code example

Without preprocess you get "unexpected token" errors when importing types, as described here: https://stackoverflow.com/questions/72846408/sveltekit-typescript-parse-error-when-importing-types/72846510#72846510

Author: stiegi

documentation/docs/25-build-and-deploy/50-adapter-static.md

@@ -14,8 +14,10 @@ Install with `npm i -D @sveltejs/adapter-static`, then add the adapter to your `
 // @errors: 2307
 /// file: svelte.config.js
 import adapter from '@sveltejs/adapter-static';
+import preprocess from 'svelte-preprocess';
 
 export default {
+  preprocess: preprocess(),
 	kit: {
 		adapter: adapter({
 			// default options are shown. On some platforms