Add platform eng post

[cnunciato]

This still needs:

• [ ] A meta description (I plucked some text from the intro for now)
• [ ] A meta image (currently placeholder)
• [ ] Social copy (left blank in the frontmatter)

cc @SaraDPH @Marlowe992

[pulumi-bot]

Your site preview for commit 94e9e602 is ready! :tada:

http://www-testing-pulumi-docs-origin-pr-12967-94e9e602.s3-website.us-west-2.amazonaws.com.