post: Agile for devs: iterate and refactor - 18 Dec

Closes #5852 (closed)

Checklist for writer

• Link to issue added, and set to close when this MR is merged
• Due date and milestone (if applicable) added for the desired publish date
• Blog post file formatted correctly, including any accompanying images
• All relevant frontmatter included
• Review app checked for any formatting issues
• Reviewed by fellow team member
• Assign to @rebecca for review

/label ~"blog post"