remark-gfm 4.0.0

Change

• b8cc334 Update @types/mdast, unified, utilities migrate: update too
• 9eb0f54 Change to use exports migrate: don’t use private APIs
• 5715c93 Change to require Node.js 16 migrate: update too

Full Changelog: https://github.com/remarkjs/remark-gfm/compare/3.0.1...4.0.0