[POC] urql for CartProvider

[lordofthecactus]

Description

urql is a lightweight graphql client for state management. https://formidable.com/open-source/urql/

This could replace our manual context updates and our reducer

This could:

• replace our manual context updates
• facilitate optimistic updates
• ~7.1kb + 6.5kb when adding the normalization. Tree shakable and both libs reuse core, so end is less.
• Compatible with svelte, and vue,

More comparisons: https://formidable.com/open-source/urql/docs/comparison/

Questions still pending:

• Works with SSR although I have not implemented