Snippet format update

To match the starter (for the migration)

snippets/join.md

@@ -1,4 +1,7 @@
-### join
+---
+title: join
+tags: array,intermediate
+---
 
 Joins all elements of an array into a string and returns this string.
 Uses a separator and an end separator.
@@ -24,4 +27,4 @@ const join = (arr, separator = ',', end = separator) =>
 join(['pen', 'pineapple', 'apple', 'pen'], ',', '&'); // "pen,pineapple,apple&pen"
 join(['pen', 'pineapple', 'apple', 'pen'], ','); // "pen,pineapple,apple,pen"
 join(['pen', 'pineapple', 'apple', 'pen']); // "pen,pineapple,apple,pen"
-```
+```