oops forgot to add the notes to the readme

Author: Rich-Harris

apps/svelte.dev/README.md

@@ -23,3 +23,7 @@ When writing content for the tutorial, you need to be aware of the differences o
 
 - When using root-relative paths, for a SvelteKit exercise the 'root' is the `static` directory inside the exercise itself, but for a Svelte exercise it is the root of the app so assets should do inside `apps/svelte.dev/static/tutorial`.
 - When importing relative assets in a Svelte exercise, Rollup inlines them into the bundle as base64
+
+### Dependencies
+
+If you look in the site's package.json you'll notice several dependencies that don't appear to be used, such as `@testing-library/svelte`. These are present because they're referenced in the docs, and Twoslash needs to be able to find type definitions in order to typecheck snippets. Installing the dependencies was deemed preferable to faking it with `declare module`, since we're liable to end up with fictional types that way.