Prepare the 3.21.0 release

Author: fabpot

CHANGELOG

@@ -1,4 +1,4 @@
-# 3.21.0 (2025-XX-XX)
+# 3.21.0 (2025-05-02)
 
  * Fix wrong array index
  * Deprecate `Template::loadTemplate()`

src/Environment.php

@@ -43,12 +43,12 @@
  */
 class Environment
 {
-    public const VERSION = '3.21.0-DEV';
+    public const VERSION = '3.21.0';
     public const VERSION_ID = 32100;
     public const MAJOR_VERSION = 3;
     public const MINOR_VERSION = 21;
     public const RELEASE_VERSION = 0;
-    public const EXTRA_VERSION = 'DEV';
+    public const EXTRA_VERSION = '';
 
     private $charset;
     private $loader;