fix: gamestop false positives (#395)

Fixed issue where gamestop would generate false positives because the string add to cart was still included even when there was no stock available.  Just added the outOfStock label to look for not available, which is actually displayed on the button.

src/store/model/gamestop.ts

@@ -5,6 +5,10 @@ export const Gamestop: Store = {
 		inStock: {
 			container: '.add-to-cart',
 			text: ['add to cart']
+		},
+		outOfStock: {
+			container: '.add-to-cart',
+			text: ['not available']
 		}
 	},
 	links: [