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/median.md

@@ -2,7 +2,7 @@
 
 Returns the median of an array of numbers.
 
-Find the middle of the array, use `Array.sort()` to sort the values.
+Find the middle of the array, use `Array.prototype.sort()` to sort the values.
 Return the number at the midpoint if `length` is odd, otherwise the average of the two middle numbers.
 
 ```js