Snippet format update

To match the starter (for the migration)

snippets/isFunction.md

@@ -1,4 +1,7 @@
-### isFunction
+---
+title: isFunction
+tags: type,function,beginner
+---
 
 Checks if the given argument is a function.
 
@@ -11,4 +14,4 @@ const isFunction = val => typeof val === 'function';
 ```js
 isFunction('x'); // false
 isFunction(x => x); // true
-```
+```