Snippet format update

To match the starter (for the migration)

snippets/unfold.md

@@ -1,4 +1,7 @@
-### unfold
+---
+title: unfold
+tags: function,array,intermediate
+---
 
 Builds an array, using an iterator function and an initial seed value.
 
@@ -17,4 +20,4 @@ const unfold = (fn, seed) => {
 ```js
 var f = n => (n > 50 ? false : [-n, n + 10]);
 unfold(f, 10); // [-10, -20, -30, -40, -50]
-```
+```