Merge branch '3.4' into 4.1

* 3.4:
  Fix docs
  enabled short array notation in CS
  [fabbot] enable short arrays
  bumped Symfony version to 3.4.22
  updated VERSION for 3.4.21
  update CONTRIBUTORS for 3.4.21
  updated CHANGELOG for 3.4.21

Author: xabbuh

Command/Command.php

@@ -380,7 +380,7 @@ public function addArgument($name, $mode = null, $description = '', $default = n
      * Adds an option.
      *
      * @param string                        $name        The option name
-     * @param string|array                  $shortcut    The shortcuts, can be null, a string of shortcuts delimited by | or an array of shortcuts
+     * @param string|array|null             $shortcut    The shortcuts, can be null, a string of shortcuts delimited by | or an array of shortcuts
      * @param int|null                      $mode        The option mode: One of the InputOption::VALUE_* constants
      * @param string                        $description A description text
      * @param string|string[]|int|bool|null $default     The default value (must be null for InputOption::VALUE_NONE)

Input/InputOption.php

@@ -34,7 +34,7 @@ class InputOption
 
     /**
      * @param string                        $name        The option name
-     * @param string|array                  $shortcut    The shortcuts, can be null, a string of shortcuts delimited by | or an array of shortcuts
+     * @param string|array|null             $shortcut    The shortcuts, can be null, a string of shortcuts delimited by | or an array of shortcuts
      * @param int|null                      $mode        The option mode: One of the VALUE_* constants
      * @param string                        $description A description text
      * @param string|string[]|int|bool|null $default     The default value (must be null for self::VALUE_NONE)
@@ -89,7 +89,7 @@ public function __construct(string $name, $shortcut = null, int $mode = null, st
     /**
      * Returns the option shortcut.
      *
-     * @return string The shortcut
+     * @return string|null The shortcut
      */
     public function getShortcut()
     {