Apple has shared new App Store marketing tools for developers to promote their apps in various ways, like generating a custom QR code.
New App Store Marketing Tools
Take advantage of new marketing resources to promote your apps around the world. You can now generate short links or embeddable code that lead to your App Store product page and display your app icon, a QR code, or an App Store badge. Download localized App Store badges, your app icon, and more.
To get started visit this web page and type in the name of your app and game. From there you can generate an app embed for your icon or download the artwork, download App Store badges, and create a QR that you can customize with your app icon and change its color.