Snippet format update

To match the starter (for the migration)

snippets/isPlainObject.md

@@ -1,4 +1,7 @@
-### isPlainObject
+---
+title: isPlainObject
+tags: type,object,intermediate
+---
 
 Checks if the provided value is an object created by the Object constructor.
 
@@ -11,4 +14,4 @@ const isPlainObject = val => !!val && typeof val === 'object' && val.constructor
 ```js
 isPlainObject({ a: 1 }); // true
 isPlainObject(new Map()); // false
-```
+```