Push container images to a private org

The access permissions in Forgejo does not allow making packages
of a user private, the only options are hide the user completely
or make packages public.  Do a workaround for this by pushing to
a private org.

.forgejo/workflows/build.yaml

@@ -3,7 +3,7 @@ on:
     branches:
       - develop
 env:
-  REGISTRY_IMAGE: ${{ vars.REGISTRY }}/${{ github.repository }}:${{ github.ref_name }}
+  REGISTRY_IMAGE: ${{ vars.REGISTRY }}/private/schedule-demo:${{ github.ref_name }}
 
 jobs:
   build: