related to #1693 changed smarty version to 4.1.0

include/smarty/docs/programmers/api-variables/variable-plugins-dir.md

@@ -0,0 +1,28 @@
+\$plugins\_dir {#variable.plugins.dir}
+==============
+
+This is the directory or directories where Smarty will look for the
+plugins that it needs. Default is `plugins/` under the
+[`SMARTY_DIR`](#constant.smarty.dir). If you supply a relative path,
+Smarty will first look under the [`SMARTY_DIR`](#constant.smarty.dir),
+then relative to the current working directory, then relative to the PHP
+include\_path. If `$plugins_dir` is an array of directories, Smarty will
+search for your plugin in each plugin directory **in the order they are
+given**.
+
+> **Note**
+>
+> For best performance, do not setup your `$plugins_dir` to have to use
+> the PHP include path. Use an absolute pathname, or a path relative to
+> `SMARTY_DIR` or the current working directory.
+
+> **Note**
+>
+> As of Smarty 3.1 the attribute \$plugins\_dir is no longer accessible
+> directly. Use [`getPluginsDir()`](#api.get.plugins.dir),
+> [`setPluginsDir()`](#api.set.plugins.dir) and
+> [`addPluginsDir()`](#api.add.plugins.dir) instead.
+
+See also [`getPluginsDir()`](#api.get.plugins.dir),
+[`setPluginsDir()`](#api.set.plugins.dir) and
+[`addPluginsDir()`](#api.add.plugins.dir).