Snippet format update

To match the starter (for the migration)

snippets/deepFlatten.md

@@ -1,4 +1,7 @@
-### deepFlatten
+---
+title: deepFlatten
+tags: array,recursion,intermediate
+---
 
 Deep flattens an array.
 
@@ -12,4 +15,4 @@ const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFla
 
 ```js
 deepFlatten([1, [2], [[3], 4], 5]); // [1,2,3,4,5]
-```
+```