Finish basic ptt implemenation

src/room/Timer.jsx

@@ -0,0 +1,37 @@
+import React, { useEffect, useState } from "react";
+
+function leftPad(value) {
+  return value < 10 ? "0" + value : value;
+}
+
+function formatTime(msElapsed) {
+  const secondsElapsed = msElapsed / 1000;
+  const hours = Math.floor(secondsElapsed / 3600);
+  const minutes = Math.floor(secondsElapsed / 60) - hours * 60;
+  const seconds = Math.floor(secondsElapsed - hours * 3600 - minutes * 60);
+  return `${leftPad(hours)}:${leftPad(minutes)}:${leftPad(seconds)}`;
+}
+
+export function Timer({ value }) {
+  const [timestamp, setTimestamp] = useState();
+
+  useEffect(() => {
+    const startTimeMs = performance.now();
+
+    let animationFrame;
+
+    function onUpdate(curTimeMs) {
+      const msElapsed = curTimeMs - startTimeMs;
+      setTimestamp(formatTime(msElapsed));
+      animationFrame = requestAnimationFrame(onUpdate);
+    }
+
+    onUpdate(startTimeMs);
+
+    return () => {
+      cancelAnimationFrame(animationFrame);
+    };
+  }, [value]);
+
+  return <p>{timestamp}</p>;
+}