Add a stock check on Wishlist so OOS products cant be added to cart from Wishlist

Added a "Notify Me" button for out-of-stock wishlist items (when the store's Notify Stock app is enabled), replacing the Add to Cart button, on both the account and shared wishlist pages.

This includes:

• "Notify Me" button for out-of-stock wishlist items

• Requires the store's Notify Stock app to be enabled

• Available on account and shared wishlist pages

How it benefits the Merchant

Prevents customers from attempting to buy out-of-stock items from their wishlist, while capturing demand for a back-in-stock notification to support future sales.

Potential FAQs

Q: Do I need the Notify Stock app for this to work?

A: Yes, the Notify Me button appears when the store's Notify Stock app is enabled.

Q: Where does this button appear?

A: On both the account wishlist page and shared wishlist pages, replacing the Add to Cart button for out-of-stock items.