Update 0239-sliding-window-maximum.js

[andynullwong]

Since JavaScript does not have a native Deque data structure, I included a 2nd solution with an array with Lazy Deletion as an alternative to the current and only solution using a Linked-List w/ custom methods. I figured this would be a useful example as it would be less verbose to implement during live coding interviews.

If you find this solution a good addition I can make another PR for Typescript as well.

• File(s) Modified: 0239-sliding-window-maximum.js
• Language(s) Used: javascript
• Submission URL: https://leetcode.com/problems/sliding-window-maximum/submissions/869504548/