push to ghcr.io

[jhrozek]

The intent is for the resulting images to be pushed to ghcr.io instead of quay as the default

[jhrozek]

@RoddieKieley I'm sorry my notes from last week are incomplete, was the intent that we do this (perhaps because of any secrets that might need to be set up or permissions) or were you going to?

No pressure at all, just making sure we're tracking things that need to be helped with.