Snippet format update

To match the starter (for the migration)

snippets/compact.md

@@ -1,4 +1,7 @@
-### compact
+---
+title: compact
+tags: array,beginner
+---
 
 Removes falsy values from an array.
 
@@ -10,4 +13,4 @@ const compact = arr => arr.filter(Boolean);
 
 ```js
 compact([0, 1, false, 2, '', 3, 'a', 'e' * 23, NaN, 's', 34]); // [ 1, 2, 3, 'a', 's', 34 ]
-```
+```