Keep syncing, even if errors are encountered

> --keep-going If any errors occur during copying of images, those errors are logged and the process continues syncing rest of the images and finally fails at the end.

Ref: https://github.com/containers/skopeo/blob/main/docs/skopeo-sync.1.md

.github/workflows/push-main.yml

@@ -190,6 +190,7 @@ jobs:
  sudo -E skopeo sync \
  --src yaml \
  --retry-times=2 \
+ --keep-going \
  --dest docker \
  /.github/promote-images.yml "${DH_IMAGE_REGISTRY}/gitpod"