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

framework/vendure/common/get-page.ts

@@ -0,0 +1,40 @@
+import { VendureConfig, getConfig } from '../api'
+
+export type Page = any
+
+export type GetPageResult<T extends { page?: any } = { page?: Page }> = T
+
+export type PageVariables = {
+  id: number
+}
+
+async function getPage(opts: {
+  url?: string
+  variables: PageVariables
+  config?: VendureConfig
+  preview?: boolean
+}): Promise<GetPageResult>
+
+async function getPage<T extends { page?: any }, V = any>(opts: {
+  url: string
+  variables: V
+  config?: VendureConfig
+  preview?: boolean
+}): Promise<GetPageResult<T>>
+
+async function getPage({
+  url,
+  variables,
+  config,
+  preview,
+}: {
+  url?: string
+  variables: PageVariables
+  config?: VendureConfig
+  preview?: boolean
+}): Promise<GetPageResult> {
+  config = getConfig(config)
+  return {}
+}
+
+export default getPage