Snippet format update

To match the starter (for the migration)

snippets/when.md

@@ -1,4 +1,7 @@
-### when
+---
+title: when
+tags: function,intermediate
+---
 
 Tests a value, `x`, against a predicate function. If `true`, return `fn(x)`. Else, return `x`. 
 
@@ -12,4 +15,4 @@ const when = (pred, whenTrue) => x => (pred(x) ? whenTrue(x) : x);
 const doubleEvenNumbers = when(x => x % 2 === 0, x => x * 2);
 doubleEvenNumbers(2); // 4
 doubleEvenNumbers(1); // 1
-```
+```