Fix a bug with nest snippet

Pass `link` to nested `nest` call.
Resolves #1116.

snippets/nest.md

@@ -15,7 +15,7 @@ Omit the third argument, `link`, to use `'parent_id'` as the default property wh
 const nest = (items, id = null, link = 'parent_id') =>
   items
     .filter(item => item[link] === id)
-    .map(item => ({ ...item, children: nest(items, item.id) }));
+    .map(item => ({ ...item, children: nest(items, item.id, link) }));
 ```
 
 ```js
@@ -28,4 +28,4 @@ const comments = [
   { id: 5, parent_id: 4 }
 ];
 const nestedComments = nest(comments); // [{ id: 1, parent_id: null, children: [...] }]
-```
+```