Map and set getters to give a way to get an item at an order

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Method to access the `nth` inserted element in a map

For example: const map = new Map(); map.set(1, 2); map.set(3, 4); console.log(map.nth(1)); // [3, 4] Preserved insertion order is a handy feature of Maps. It makes them more useful for building caches with eviction policies. For example, you can build an LRU cache by deleting and re-inserting items when they are accessed. While implementing the SIEVE algorithm in JS, I noticed that an .nth() method would be handy. Without it, I need to track insertion order in a seperate array, OR copy the ke…