(docs) update TS setup instructions

- remove depracted type/lang options
- differentiate between ESM and CJS style projects

docs/preprocessors/typescript.md

@@ -12,22 +12,25 @@ Adding it to an existing project? [The official blog post explains how to do it]
 
 #### 2. Getting it to work in the editor
 
-To tell us to treat your script tags as typescript, add a `type` or `lang` attribute to your script tags like so:
+To tell us to treat your script tags as typescript, add a `lang` attribute to your script tags like so:
 
 ```html
-<!-- Add type="text/typescript" -->
-<script type="text/typescript">
-    export let name: string;
-</script>
-
-<!-- Or add lang="typescript" or lang="ts" -->
-<script lang="typescript">
+<script lang="ts">
     export let name: string;
 </script>
 ```
 
-You may optionally want to add a `svelte.config.js` file - but it is not required as long as you only use TypeScript.
+You may optionally want to add a `svelte.config.js` file - but it is not required as long as you only use TypeScript.Depending on your setup, this config file needs to be written either in ESM-style or CJS-Style.
 
+ESM-style (for everything with `"type": "module"` in its `package.json`, like SvelteKit):
+```js
+import sveltePreprocess from 'svelte-preprocess';
+
+export default {
+    preprocess: sveltePreprocess()
+};
+```
+CJS-style:
 ```js
 const sveltePreprocess = require('svelte-preprocess');