Update README.md

Author: dash8x

README.md

@@ -13,6 +13,7 @@
 <!-- TOC -->
 * [eFaas Laravel Socialite](#efaas-laravel-socialite)
   * [Requirements](#requirements)
+  * [Upgrading](#upgrading)
   * [Installation](#installation)
     * [Add configuration to your `.env` file](#add-configuration-to-your-env-file)
     * [Publishing the config file](#publishing-the-config-file)
@@ -56,6 +57,10 @@ This package requires the following:
 - PHP 7.4 or higher
 - ext-openssl PHP extension
 
+## Upgrading
+
+Please see the [Upgrade Guide](UPGRADE.md) on how to upgrade the package.
+
 ## Installation
 
 For Laravel 6.0+, you can install the package via `composer`: