Snippet format update

To match the starter (for the migration)

snippets/btoa.md

@@ -1,4 +1,7 @@
-### btoa
+---
+title: btoa
+tags: node,string,utility,beginner
+---
 
 Creates a base-64 encoded ASCII string from a String object in which each character in the string is treated as a byte of binary data.
 
@@ -10,4 +13,4 @@ const btoa = str => Buffer.from(str, 'binary').toString('base64');
 
 ```js
 btoa('foobar'); // 'Zm9vYmFy'
-```
+```