Update CHANGELOG.md

Author: filrak

CHANGELOG.md

@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [1.8.3] - 2019.03.03
 
 ### Added
+- Payment Request API integration - @qiqqq (#2306)
 - New reactive helper to check online state. Usage: `import { onlineHelper } from '@vue-storefront/core/helpers'` and then `onlineHelper.isOnline` - @patzick (#2510)
 - Cart count config, allows you to display the item count instead of a sum of the item quantities - @pauluse (#2483)
 - Video support in Product Gallery component. - @rain2o (#2433)