Vendure provider (#223)

* Minimal list/detail views working with Vendure

* Implement useCart/useAddItem

* Implement useUpdateItem & useRemoveItem

* Implement useSearch

* Add operations codegen, tidy up

* Dummy checkout page

* Implement auth/customer hooks

* Use env var for Shop API url

* Add some documentation

* Improve error handling

* Optimize preview image size

* Fix accidental change

* Update Vendure provider to latest changes

* Vendure provider: split out gql operations, remove unused files

* Update Vendure provider readme

* Add local next.config to Vendure provider, update docs

* Update to use demo server

* Fix build errors

* Use proxy for vendure api

* Simplify instructions in Vendure readme

* Refactor Vendure checkout api handler

* Improve image quality

package.json

@@ -9,6 +9,7 @@
     "prettier-fix": "prettier --write .",
     "find:unused": "next-unused",
     "generate": "graphql-codegen",
+    "generate:vendure": "graphql-codegen --config framework/vendure/codegen.json",
     "generate:definitions": "node framework/bigcommerce/scripts/generate-definitions.js"
   },
   "sideEffects": false,