[docs] Add a blog post about type classes

[jackkoenig]

Contributor Checklist

Type of Improvement

• Documentation or website-related

Desired Merge Strategy

• Squash

Release Notes

Reviewer Checklist (only modified by reviewer)

• [x] Did you add the appropriate labels? (Select the most appropriate one based on the "Type of Improvement")
• [ ] Did you mark the proper milestone (Bug fix: 3.6.x, 5.x, or 6.x depending on impact, API modification or big change: 7.0)?
• [ ] Did you review?
• [ ] Did you check whether all relevant Contributor checkboxes have been checked?
• [ ] Did you do one of the following when ready to merge:
  • [ ] Squash: You/ the contributor Enable auto-merge (squash) and clean up the commit message.
  • [ ] Merge: Ensure that contributor has cleaned up their commit history, then merge with Create a merge commit.