versioned images in next/public/.versioned_images/
added a new step version_images in update_version which will copy the public/images/ to next/public/.versioned_images/<version>
we will only version an image when:
- use <Image> component in mdx
- on non-master version
- in public/images/ dir
so we don't need to backfill for the old versions - as the old mdx don't use <Image> component