Fix product schema offers declaration description

[moorscode]

Summary

The described property cannot be a list, but has to be a reference to an offer (or aggregate offer as that is a derivative of an offer).

See the Schema docs for the declaration: https://schema.org/Product

The example also shows an object with an @id instead of a list.

Quality assurance

• I have altered a filename.
  • I have adjusted the ID property accordingly and updated all internal links.
  • I have added the redirect to the _redirects file in the root of the project.

[d-claassen]

Hey there @moorscode. Thanks for taking the time to add your contribution! 😃

The schema.org data model is really flexible, and will almost anywhere accept both a single instance or multiple instances in an array. As an example, take a look at the review property on the Product type, which can also take a list of multiple Review instances. In fact, the Schema documentation about Product that you linked has an example (Example 2) showing the property offers with a list of Offer instances. Note this example shows both the property with a single instance and an array of instances, through the AggregateOffer object, but in the Schema data model there's no difference between the two properties depending on their type.

In case you're interested, we'll definitely be open to accepting a contribution to reflect both possibilities are acceptable: Either a reference by ID, or an array of such references.