Hello! Really excited by this project. Found a small issue regarding the docker exporter.

Using the docker exporter doesn't result in the image being loaded with an appropriate created time.

> docker image ls
# ...
buildkit0  latest  7a18bfe39b22  292 years ago  86.8MB

I did a little groking of my own. Tried update the OCI index record with the OCI spec annotation for created and no luck. Looking at the Docker daemons tarexport it appears they don't fully support OCI and I see that docker load --oci is actually a WIP moby/moby#33355.

So I assume the config exported (the one the manifest points to) should be marshaled to the type defined here: https://github.com/moby/moby/blob/master/image/image.go#L35 ? Is that correct?

p.s. wrote a little blog post about getting started with this project, mostly just a walkthrough based on the docs :) hope it makes sense http://george.macro.re/posts/getting-started-with-buildkit/