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/nthElement.md

@@ -2,7 +2,7 @@
 
 Returns the nth element of an array.
 
-Use `Array.slice()` to get an array containing the nth element at the first place.
+Use `Array.prototype.slice()` to get an array containing the nth element at the first place.
 If the index is out of bounds, return `undefined`.
 Omit the second argument, `n`, to get the first element of the array.