Draft: Blog Post - How We Migrated Millions of Container Images

Closes #14122 (closed)

Checklist for writer

• Link to issue added, and set to close when this MR is merged
• Due date and marketing milestone (e.g. Mktg: 2021-03-28) added to title for the desired publish date
• If time sensitive
  • Added ~"priority" label
  • Mentioned @sgittlen to give her a heads up ASAP
• Blog post file formatted correctly, including uploading and embedding in markdown any accompanying images
• All relevant frontmatter included
• Review app checked for any formatting issues
• Reviewed by fellow team member(s)
• Reviewer(s) marked approved before sending to blog team
  • Any required internal or external approval for this blog post has been granted (please leave a comment with details)
• Assign to @Sgittlen for final review

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