E2E localization design

[elisenyang]

We need to figure out how localization works across components (ShopifyProvider, CartProvider, etc.), re-design where it's confusing, and provide docs/tutorials on how to implement and best practices.

Related issues:

• [BUG] CartProvider not taking languageCode into account hydrogen-react#42
• [BUG] Cart doesn't use default Hydrogen localisation #622

[rennyG]

Would this be covered by Hydrogen 2.0 documentation if we're providing a guide on that? cc. @blittle

[elisenyang]

changes to be made:

• deprecate shopifyConfig prop (remove from docs)
• add all props as standalone
• add countryCode and languageCode props as required and type string
• don't include locale and make sure to generate this for useMoney

[frehner]

<ShopifyProvider/> has been updated to fit the requirements listed above; the last part of this ticket is to update Cart stuff to make sure it works well with it, too.