I added a basic entry for the resize transform, it could use an expansion to offer more efficient ways to do the resize once, rather than doing it on the go.
If you’d like to make a PR with various ways one could do the resize on the filesystem once, instead of re-doing it on every run, that would be great. I usually use imagemagick but I don’t know if it’s still the best method. There are a few threads about the subject matter here on the forums, so perhaps if you could make a summary of the best methods including the nuances of resizing mixed sized images, etc. that would be useful to have documented in one place.