add changeset

Author: quantizor

.changeset/upgrade-react-19-types.md

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+---
+'markdown-to-jsx': major
+---
+
+Upgrade to React 19 types
+
+- Update to `@types/react@^19.2.2` and `@types/react-dom@^19.2.2`
+- Use `React.JSX.*` namespace instead of `JSX.*` for React 19 compatibility