F/product actions component

[brynn]

• [x] modular ProductActions component
• [x] use inventory as bound on quantity selector
• [x] show sold out if inventory = 0
• [x] link entire product card to single product
• [x] utility function for formatting products into correct number of columns (used in AllProducts and Cart)
• [x] utility function for summing total cost
• [x] updates seed data to include a product with inventory 5 and one with 0