Not able to filter ImageAssets by MediaTag

[fostimus]

In the Media Library for Sanity, there's a way to tag photos. It's accessible via GROQ, and we are able to pull images for only a specific tag.

In Gatsby, that's not possible. Here are the fields for ImageAssets from the source plugin:

I can use the API client, but that defeats the purpose of a source plugin for Gatsby :/