minor improvements

config/app.php

@@ -102,6 +102,8 @@ return [
     | Ensure it is uppercase and reflects the 'code' column of the
     | countries table.
     |
+    | for example: DE EN FR
+    | (use capital letters!)
     */
 
     'default_country' => null,

packages/Webkul/Checkout/src/Cart.php

@@ -764,7 +764,7 @@ class Cart
 
                     function __construct()
                     {
-                        $this->country = config('app.default_country');
+                        $this->country = strtoupper(config('app.default_country'));
                     }
                 };
             }