Adds plugin for Contentful synchronization (#75)

Adds plugin for Contentful

Will create product and product variants in Contentful, when created in Medusa

Closes #47

packages/medusa-plugin-contentful/src/api/index.js

@@ -0,0 +1,10 @@
+import { Router } from "express"
+import hooks from "./routes/hooks"
+
+export default (container) => {
+  const app = Router()
+
+  hooks(app)
+
+  return app
+}