Improve StoreConfig example in README.md

This commit enhances the StoreConfig example in the README by providing
more precise information about the location of the issuer ID in App Store
Connect.

README.md

@@ -165,7 +165,7 @@ func main() {
 		KeyContent: []byte(ACCOUNTPRIVATEKEY),  // Loads a .p8 certificate
 		KeyID:      "FAKEKEYID",                // Your private key ID from App Store Connect (Ex: 2X9R4HXF34)
 		BundleID:   "fake.bundle.id",           // Your app’s bundle ID
-		Issuer:     "xxxxx-xx-xx-xx-xxxxxxxxxx",// Your issuer ID from the Keys page in App Store Connect (Ex: "57246542-96fe-1a63-e053-0824d011072a")
+		Issuer:     "xxxxx-xx-xx-xx-xxxxxxxxxx",// Your issuer ID from App Store Connect (Users and Access > Integrations > In-App Purchase)(Ex: "57246542-96fe-1a63-e053-0824d011072a")
 		Sandbox:    false,                      // default is Production
 	}
 	originalTransactionId := "FAKETRANSACTIONID"