docs: link to list of community preprocessors (#4817)

site/content/docs/04-compile-time.md

@@ -183,6 +183,10 @@ const ast = svelte.parse(source, { filename: 'App.svelte' });
 
 ### `svelte.preprocess`
 
+A number of [community-maintained preprocessing plugins](https://github.com/sveltejs/integrations#preprocessors) are available to allow you to use Svelte with tools like TypeScript, PostCSS, SCSS, and Less.
+
+You can write your own preprocessor using the `svelte.preprocess` API.
+
 ```js
 result: {
 	code: string,