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/functions.md

@@ -4,7 +4,7 @@ Returns an array of function property names from own (and optionally inherited)
 
 Use `Object.keys(obj)` to iterate over the object's own properties.
 If `inherited` is `true`, use `Object.get.PrototypeOf(obj)` to also get the object's inherited properties.
-Use `Array.filter()` to keep only those properties that are functions.
+Use `Array.prototype.filter()` to keep only those properties that are functions.
 Omit the second argument, `inherited`, to not include inherited properties by default.
 
 ```js