User reviews system

[gacelita]

Reviews should contain "title", "description", "images" and "rating" fields. The plugin should show the reviews for a product in the product page, and allow the user to do basic CUD operations (create, update, delete) on their own reviews. An administration section should be added for listing the reviews. Reviews should be able to be moderated by a privileged user.

[gacelita]

Added the beginner-friendly tag because this is basically just doing the same as done in other parts of the app: create an entity type, create an admin section for it, create a backend event, create a component that uses that backend event.