related to #1693 changed smarty version to 4.1.0

include/smarty/docs/programmers/plugins/plugins-writing.md

@@ -0,0 +1,36 @@
+Writing Plugins {#plugins.writing}
+===============
+
+Plugins can be either loaded by Smarty automatically from the filesystem
+or they can be registered at runtime via one of the register\_\* API
+functions. They can also be unregistered by using unregister\_\* API
+functions.
+
+For the plugins that are registered at runtime, the name of the plugin
+function(s) does not have to follow the naming convention.
+
+If a plugin depends on some functionality provided by another plugin (as
+is the case with some plugins bundled with Smarty), then the proper way
+to load the needed plugin is this:
+
+
+    <?php
+    function smarty_function_yourPlugin(array $params, Smarty_Internal_Template $template)
+    {
+      // load plugin depended upon
+      $template->smarty->loadPlugin('smarty_shared_make_timestamp');
+      // plugin code
+    }
+    ?>
+
+        
+
+As a general rule, the currently evaluated template\'s
+Smarty\_Internal\_Template object is always passed to the plugins as the
+last parameter with two exceptions:
+
+-   modifiers do not get passed the Smarty\_Internal\_Template object at
+    all
+
+-   blocks get passed `$repeat` after the Smarty\_Internal\_Template
+    object to keep backwards compatibility to older versions of Smarty.