Support Stripe usage based pricing

[iaminawe]

Excellent work, this looks like a really useful setup for running small stores without requiring their own database.
Thanks for all the teams work so far.

I would love to see usage based pricing being supported to accommodate for things like tier pricing where the unit cost changes based on the quantity of items added to the cart.

My use case would be for a wholesale type store where the price gets cheaper the more items that you add - I know that Stripe supports this in their checkout and I would be curious to know if this is something that could be exposed at the product level so the pricing could dynamically update based on the quantity.

Here is an article on how the stripe variable pricing works.
https://stripe.com/en-ca/resources/more/usage-based-pricing-101-what-it-is-and-strategies-to-implement-it