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/intersection.md

@@ -2,7 +2,7 @@
 
 Returns a list of elements that exist in both arrays.
 
-Create a `Set` from `b`, then use `Array.filter()` on `a` to only keep values contained in `b`.
+Create a `Set` from `b`, then use `Array.prototype.filter()` on `a` to only keep values contained in `b`.
 
 ```js
 const intersection = (a, b) => {