API changes

• Added a root query field shopifyApp: ShopifyApp! which fetches details about the Rye's Shopify App. Currently, it includes the single field installationLink(storeCanonicalDomain: String!): ShopifyAppInstallationLink! that crafts a Rye App installation link for the provided Shopify store.
• Added a root query field environmentToken. This query is used by the RyePay package and should not be used by developers directly.
• Added id field to AmazonVariant that represents ASIN of the variant.
• postalCode of BuyerIdentityInput has become optional.
• Added a new generateJWT: () => Promise<string>param to RyePay::init method. It allows providing a function that generates JWT for authorization and can be passed instead of apiKey

Resolved issues

• Fixed cannot read properties undefined (reading 'currency') exception occurred when querying Cart:cost field for an already submitted cart.