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/groupBy.md

@@ -2,8 +2,8 @@
 
 Groups the elements of an array based on the given function.
 
-Use `Array.map()` to map the values of an array to a function or property name.
-Use `Array.reduce()` to create an object, where the keys are produced from the mapped results.
+Use `Array.prototype.map()` to map the values of an array to a function or property name.
+Use `Array.prototype.reduce()` to create an object, where the keys are produced from the mapped results.
 
 ```js
 const groupBy = (arr, fn) =>