[feature request] optional extra tags for set icon
Hi,
with all the new promo types using the same set symbol, it would be nice if it was possible to specify a tag to modify the default set icon and append a small letter or symbol. In this way for example one could understand that a card edition is the prerelease one and not the main edition.

I see it used on mkm and a few other sites, i thought it would be nice to have a configuration option to add it.

Example with a default and prerelease (star)
<img width="83" alt="Screen Shot 2020-09-02 at 11 54 45" src="https://user-images.githubusercontent.com/1374357/91967176-dc3c7300-ece0-11ea-846e-a9d094124e37.png">

Example with default, promo pack (pw symbol), prerelease (star), boosterfun (C)
<img width="161" alt="Screen Shot 2020-09-02 at 11 57 11" src="https://user-images.githubusercontent.com/1374357/91967457-4523eb00-ece1-11ea-9681-5174c848ce6d.png">

they don't have to be these symbol necessarily, as long as it's something users can relate to
I hope this feature will be considered a future release, thanks