v0.10 Release Tasks

[ryyppy]

• [x] Port to ReScript syntax
• [x] Align naming / terminologies
• [x] Remove legacy code (see Changes.md for details)
• [x] Upgrade to [email protected]
• [x] Align upcoming docs for [email protected] (available here)
• [ ] Write migration-guide for [email protected] -> [email protected]
• [x] Try rescript-react in existing codebases before official release
• [x] Release [email protected]
• [x] Add a note on reason-react for new users