Update README.md

README.md

@@ -20,6 +20,7 @@ Like what we do? Want to join us? Check out our job listings on our [career page
 
 * [Overview](#overview)
 * [Support](#we-are-here-to-help)
+* [Functionalities](#functionalities)
 * [Installation](#installation)
   * [Customization](#customization)
   * [Testing](#testing)
@@ -40,6 +41,10 @@ This **open-source plugin was developed to help the Sylius community**. If you h
 
 [![](https://bitbag.io/wp-content/uploads/2020/10/button-contact.png)](https://bitbag.io/contact-us/?utm_source=github&utm_medium=referral&utm_campaign=plugins_przelewy24)
 
+# Functionalities
+
+All main functionalities of the plugin are described [here.](https://github.com/BitBagCommerce/SyliusPrzelewy24Plugin/blob/master/doc/functionalities.md)
+
 ## Installation
 
 ```