Snippet format update

To match the starter (for the migration)

snippets/castArray.md

@@ -1,4 +1,7 @@
-### castArray
+---
+title: castArray
+tags: utility,array,type,beginner
+---
 
 Casts the provided value as an array if it's not one.
 
@@ -11,4 +14,4 @@ const castArray = val => (Array.isArray(val) ? val : [val]);
 ```js
 castArray('foo'); // ['foo']
 castArray([1]); // [1]
-```
+```