4.0.0

• b9a87e9 Update unist-util-visit
  (breaking, potentially, if you or your dependents use typescript)
• f69f966 Update unist-util-is
  (breaking, potentially, if you or your dependents use typescript)
• eddf7ff Refactor prose
• 31d1cac Update metadata
• 44092df Add funding field to package.json