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/untildify.md

@@ -2,7 +2,7 @@
 
 Converts a tilde path to an absolute path.
 
-Use `String.replace()` with a regular expression and `OS.homedir()` to replace the `~` in the start of the path with the home directory.
+Use `String.prototype.replace()` with a regular expression and `OS.homedir()` to replace the `~` in the start of the path with the home directory.
 
 ```js
 const untildify = str => str.replace(/^~($|\/|\\)/, `${require('os').homedir()}$1`);