[FIX] index, reactivity: export reactive function in index

src/index.ts

@@ -55,7 +55,7 @@ export { status } from "./component/status";
 export { Portal } from "./portal";
 export { Memo } from "./memo";
 export { css, xml } from "./tags";
-export { useState } from "./reactivity";
+export { useState, reactive } from "./reactivity";
 export { useEffect, useEnv, useExternalListener, useRef, useSubEnv } from "./hooks";
 export { EventBus, whenReady, loadFile, markup } from "./utils";