Add doc to script file

src/hooks/useAppState.ts

@@ -1,3 +1,14 @@
+/**
+ * Application State Hook
+ *
+ * Manages global application state with localStorage persistence.
+ * Provides type-safe state updates for nested objects and automatic
+ * state saving on changes.
+ *
+ * @author Andreas Weyer
+ * @license MIT
+ */
+
 import React from 'react';
 import { LOCAL_STORAGE_KEY, getDefaultState, type AppState } from '../constants/defaults';