Add docblock info about options for DefaultPasswordHasher.

src/Auth/DefaultPasswordHasher.php

@@ -25,6 +25,13 @@ class DefaultPasswordHasher extends AbstractPasswordHasher {
 /**
  * Default config for this object.
  *
+ * ### Options
+ *
+ * - `hasType` - Hashing algo to use. Valid values are those supported by `$algo`
+ *   argument of `password_hash()`. Defaults to `PASSWORD_DEFAULT`
+ * - `hashOptions` - Associative array of options. Check the PHP manual for
+ *   supported options for each hash type. Defaults to empty array.
+ *
  * @var array
  */
 	protected $_defaultConfig = [