Add mapString, fix dig

snippets/dig.md

@@ -5,7 +5,7 @@ Returns the target value in a nested JSON object, based on the given key.
 Use the `in` operator to check if `target` exists in `obj`.
 If found, return the value of `obj[target]`, otherwise use `Object.values(obj)` and `Array.reduce()` to recursively call `dig` on each nested object until the first matching key/value pair is found.
 
-```
+```js
 const dig = (obj, target) =>
   target in obj
     ? obj[target]
@@ -17,7 +17,7 @@ const dig = (obj, target) =>
         }, undefined);
 ```
 
-```
+```js
 const data = {
   level1:{
     level2:{