chore: add types for react demo (#8517)

chore: add types for react demo

app/react/demo.d.ts

@@ -0,0 +1,32 @@
+import React from 'react';
+import PropTypes from 'prop-types';
+
+declare const Welcome: {
+    ({ showApp }: {
+        showApp: () => void;
+    }): JSX.Element;
+    displayName: string;
+    propTypes: {
+        showApp: PropTypes.Requireable<(...args: any[]) => any>;
+    };
+    defaultProps: {
+        showApp: any;
+    };
+};
+
+declare const Button: {
+    ({ children, onClick, }: {
+        children: React.ReactNode;
+        onClick: (event: React.MouseEvent<HTMLElement, MouseEvent>) => void;
+    }): JSX.Element;
+    displayName: string;
+    propTypes: {
+        children: PropTypes.Validator<PropTypes.ReactNodeLike>;
+        onClick: PropTypes.Requireable<(...args: any[]) => any>;
+    };
+    defaultProps: {
+        onClick: () => void;
+    };
+};
+
+export { Welcome, Button };