Sometimes we want people to test features in PRs and
not everyone is used to using git, build go and docker.
This commit builds docker containers and pushes them to
GHCR (not dockerhub) for testing on pushes to branches
that has open pull requests to main using Ko.
This is configured to mimic the debug images produced
by goreleaser.
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
