Tpl: add register_modifier() method

src/Tpl.php

@@ -233,6 +233,16 @@ class Tpl {
     self :: $smarty -> registerPlugin("function", $name, $callable);
   }
 
+  /**
+   * Register a modifier usable from template files
+   * @param string $name The modifier name
+   * @param callable $callable The modifier function
+   * @return void
+   */
+  public static function register_modifier($name, $callable) {
+    self :: $smarty -> registerPlugin("modifier", $name, $callable);
+  }
+
   /**
    * Register a class usable from template files
    * @param string $class_name The class name