This updates Makefile targets to build images using `docker buildx
build` to use `ko build` instead.
End-to-end tests are accomplished by building and loading the image
directly into the KinD cluster via ko.
Also:
- use GitHub Actions token to push to ghcr.io (setup-ko sets this up for us)
- allow forks to push to their forked repo's packages (useful for testing)
Signed-off-by: Jason Hall <jason@chainguard.dev>
Signed-off-by: Jason Hall <jason@chainguard.dev>
