Add "Cost Per Item" Field from Shopify#808

Description:
I am using Windsor for pulling data from Shopify to MySQL. Currently, there is a specific field in Shopify called “cost per item” that is crucial for my data analysis and reporting. Unfortunately, this field does not exist in Windsor at the moment.

Use Case:
The “cost per item” field is essential for accurately calculating profit margins, cost analysis, and inventory valuation. Including this field in Windsor will greatly enhance the utility of the data extracted from Shopify, allowing for more comprehensive financial reporting and decision-making.

I have attached screenshot from shopify for better understanding.

Thank you for your attention to this matter.

If this helps, it is similar to line_item__variant_unit_cost in the line item table, but I need its latest value in the product table.

Cost field: https://windsor.ai/data-field/shopify/#product_variant_inventory_item_cost

Also additional “product variant inventory item” fields were added. Such as:
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_sku
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_country_code_of_origin
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_province_code_of_origin
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_harmonized_system_code
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_created_at
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_updated_at
https://windsor.ai/data-field/shopify/#product_variant_inventory_item_requires_shipping

Thank you !!!