Add `Product.breadcrumbs`and `Category.breadcrumbs` feature

[pkarw]

What is the motivation for adding / enhancing this feature?

Having breadcrumbs generated by the API instead of the frontend app is always a nice optimization. We should move the business logick from vue-storefront for that and create new function inside Product and Category resolvers:

• category breadcrumbs logic
• product breadcrumbs logic

The schema for breadcrumbs should be like:

breadcrumbs: [CategoryBinding]

The CategoryBinding is defined inside the Product type.

What are the acceptance criteria

• Product.breadcrumbs and Category.breadcrumbs available for query

[gibkigonzo]

closed by #71