Snippet format update

To match the starter (for the migration)

snippets/symmetricDifference.md

@@ -1,4 +1,7 @@
-### symmetricDifference
+---
+title: symmetricDifference
+tags: array,math,intermediate
+---
 
 Returns the symmetric difference between two arrays, without filtering out duplicate values.
 
@@ -15,4 +18,4 @@ const symmetricDifference = (a, b) => {
 ```js
 symmetricDifference([1, 2, 3], [1, 2, 4]); // [3, 4]
 symmetricDifference([1, 2, 2], [1, 3, 1]); // [2, 2, 3]
-```
+```