Avoid confusing prototype methods for static methods

Correct: `Array.from()` (it’s a static method)
Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method)

This patch uses the common `#` syntax to denote `.prototype.`.

snippets/uniqueSymmetricDifference.md

@@ -2,7 +2,7 @@
 
 Returns the unique symmetric difference between two arrays, not containing duplicate values from either array.
 
-Use `Array.filter()` and `Array.includes()` on each array to remove values contained in the other, then create a `Set` from the results, removing duplicate values.
+Use `Array.prototype.filter()` and `Array.prototype.includes()` on each array to remove values contained in the other, then create a `Set` from the results, removing duplicate values.
 
 ```js
 const uniqueSymmetricDifference = (a, b) => [