[FEATURE] Document how to use docker buildx --push to push into k3d registry

[schlichtanders]

Hi there,

I am usually using docker buildx ... --push . to build and push immediately. It seems this is not working with k3d registry. I get the following error

> exporting to image:
------
ERROR: failed to solve: failed to push k3d-registry.localhost:12345/mycontainer:latest: failed to do request: Head "https://k3d-registry.localhost:12345/v2/mycontainer/blobs/sha256:12345678123567128351627841267531627835162783": dial tcp: lookup k3d-registry.localhost on 123.456.789.0: no such host

My Workaround: using docker buildx ... --load . and then a manual push works.

It would be great if docker buildx could directly push to the k3d registry, which is probably much quicker for local development.
I guess it is already possible, but somehow hard to find how to do it.

[schlichtanders]

it might be related to this docker issue docker/buildx#94

[schlichtanders]

I just was able to push using the default builder (with driver "docker").

There seems to have been a confusion for myself - I've used driver "docker-container" all the time, which is not only slower, but also has some further missing support like this.

Lovely that it already works. Still it probably would be great to add a section to the documentation about this