Add ability to fetch replaced images by listing_image_id

[emergingdzns]

In OpenAPI V2, when you include the MainImage association, it will return the image that was the primary image on the listing at the time of the transaction.

In OpenAPI V3, the associations are no longer there, but it does provide a listing_image_id as part of the transaction object. However, the only way to fetch this image is to call getListingImage. But in some cases, the image is no longer associated to the listing (replaced by the show owner). In OpenAPI V2 this wasn't an issue because the image object still exists in Etsy.

Since we no longer have the associations (includes) on transactions could you provide a more generic get image function that will fetch an image by id but without needing the listing id, or with the listing id and being able to pull the "deleted" image.

Thanks!