updated nextjs example with app router

app/src/ui/hooks/use-event.ts

@@ -4,15 +4,15 @@
 // there is no lifecycle or Hook in React that we can use to switch
 // .current at the right timing."
 // So we will have to make do with this "close enough" approach for now.
-import { useInsertionEffect, useRef } from "react";
+import { useEffect, useRef } from "react";
 
 export const useEvent = <Fn>(fn: Fn | ((...args: any[]) => any) | undefined): Fn => {
    const ref = useRef([fn, (...args) => ref[0](...args)]).current;
    // Per Dan Abramov: useInsertionEffect executes marginally closer to the
    // correct timing for ref synchronization than useLayoutEffect on React 18.
    // See: https://github.com/facebook/react/pull/25881#issuecomment-1356244360
-   useInsertionEffect(() => {
+   useEffect(() => {
       ref[0] = fn;
-   });
+   }, []);
    return ref[1];
 };