update reaction commerce (renamed to Mailchimp Open Commerce), update links

- ref. https://github.com/awesome-selfhosted/awesome-selfhosted/issues/2266

README.md

@@ -801,6 +801,7 @@ _Related: [Community-Supported Agriculture (CSA)](#community-supported-agricultu
 - [CoreShop](https://www.coreshop.org) - CoreShop is a e-commerce plugin for Pimcore. ([Source Code](https://github.com/coreshop/CoreShop)) `GPL-3.0` `PHP`
 - [Drupal Commerce](https://drupalcommerce.org) - Drupal Commerce is a popular e-commerce module for Drupal CMS, with support for dozens of payment, shipping, and shopping related modules. ([Source Code](https://github.com/drupalcommerce/commerce)) `GPL-2.0` `PHP`
 - [Magento Open Source](https://github.com/magento/magento2) - Leading provider of open omnichannel innovation. `OSL-3.0` `PHP`
+- [Mailchimp Open Commerce](https://mailchimp.com/developer/open-commerce/) - Customizable, real-time reactive, Javascript commerce platform (formerly Reaction Commerce). ([Source Code](https://github.com/reactioncommerce/reaction)) `GPL-3.0` `Nodejs`
 - [MedusaJs](https://medusajs.com/) - Medusa is an open-source headless commerce engine that enables developers to create amazing digital commerce experiences. ([Demo](https://demo.medusajs.com/a/orders?offset=0&limit=15), [Source Code](https://github.com/medusajs/medusa)) `MIT` `Nodejs`
 - [Microweber](https://microweber.com/) - Drag and Drop CMS and online shop. ([Demo](https://demo.microweber.org/), [Source Code](https://github.com/microweber/microweber)) `Apache-2.0` `PHP`
 - [Open Source POS](https://github.com/opensourcepos/opensourcepos) - Open Source Point of Sale is a web based point of sale system. `MIT` `PHP`
@@ -808,7 +809,6 @@ _Related: [Community-Supported Agriculture (CSA)](#community-supported-agricultu
 - [OXID eShop](https://oxidforge.org/en/) - OXID eShop is a flexible open source e-commerce software with a wide range of functionalities. ([Source Code](https://github.com/OXID-eSales/oxideshop_ce)) `GPL-3.0` `PHP`
 - [PrestaShop](https://www.prestashop.com/) - PrestaShop offers a free, open-source and fully scalable e-commerce solution. ([Demo](https://demo.prestashop.com/), [Source Code](https://github.com/PrestaShop/PrestaShop)) `OSL-3.0` `PHP`
 - [Pretix](https://pretix.eu/) - Django based ticket sales platform for events. ([Source Code](https://github.com/pretix)) `Apache-2.0` `Python`
-- [Reaction Commerce](https://reactioncommerce.com/) - Customizable, real-time reactive, Javascript commerce platform. ([Source Code](https://github.com/reactioncommerce/reaction)) `GPL-3.0` `Nodejs`
 - [s-cart](https://s-cart.org/) - S-Cart is a free e-commerce website project for individuals and businesses, built on top of Laravel Framework. ([Demo](https://demo.s-cart.org/), [Source Code](https://github.com/s-cart/s-cart)) `MIT` `PHP`
 - [Saleor](https://saleor.io) - Django based open-sourced e-commerce storefront. ([Demo](https://demo.getsaleor.com/), [Source Code](https://github.com/mirumee/saleor)) `BSD-3-Clause` `Python`
 - [Shopware Community Edition](https://www.shopware.com/community/) - PHP based open source e-commerce software made in Germany. ([Demo](https://www.shopware.com/en/test-demo/), [Source Code](https://github.com/shopware/platform)) `MIT` `PHP`