Feature request: be able to specify size of thumbnail

[blitzmann]

For our use case, we only have a full size image, no thumbnail. So we use the fullsize image as the thumbnail. But by default, the image is displayed as the dimensions of the thumbnail, regardless of it's container size. This is way too large for our purposes. We need to restrict the size of the displayed image, but there doesn't seem to be a way to do this out of the box.

The work around is to create an ::ng-deep .ngxImageZoomThumbnail style to target the inner thumbnail image. I feel that this is a work around rather than a true fix. If this workaround is the intended way, I would request documentation be added that describes it (maybe in a FAQ). Example using my avatar:

https://stackblitz.com/edit/angular-ivy-czc2dm?file=src%2Fapp%2Fapp.component.ts

[wittlock]

duplicate of #64 - closing this issue in favor of that one