Add implementation of Shopify scraper.

[AbdElRhmanArafa]

1. scrape_products: fall back to parsing the HTML if the JSON data is not available, since not all websites expose product JSON (it can be enabled or disabled by the website owner).

There are two test cases:

• allbirds.com: JSON is available, so no fallback is used.
• gymshark.com: No JSON is available, so it falls back to HTML parsing.

2. scrape_catalog: I couldn't find a fallback url that works consistently across all store domains, so I didn't implement one.