presence-related fixes (#1361)

This fixes a bug where creating a page would fail if there were multiple
pages with the same index.

This also changes the store to use a throttled version of
requestAnimationFrame. This should be good for relieving backpressure in
situations where the store is updated many times in quick succession. It
also makes testing a lot easier since it has the mocking logic built in.

### Change Type

- [x] `patch` — Bug Fix


### Release Notes

- Fix a bug where creating a page could throw an error in some
multiplayer contexts.

packages/utils/src/lib/raf.ts

@@ -0,0 +1,67 @@
+const isTest = () =>
+	typeof process !== 'undefined' &&
+	process.env.NODE_ENV === 'test' &&
+	// @ts-expect-error
+	!globalThis.__FORCE_RAF_IN_TESTS__
+
+const rafQueue: Array<() => void> = []
+
+const tick = () => {
+	const queue = rafQueue.splice(0, rafQueue.length)
+	for (const fn of queue) {
+		fn()
+	}
+}
+
+let frame: number | undefined
+
+function raf() {
+	if (frame) {
+		return
+	}
+
+	frame = requestAnimationFrame(() => {
+		frame = undefined
+		tick()
+	})
+}
+
+/**
+ * Returns a throttled version of the function that will only be called max once per frame.
+ * @param fn - the fun to return a throttled version of
+ * @returns
+ * @internal
+ */
+export function rafThrottle(fn: () => void) {
+	if (isTest()) {
+		return fn
+	}
+
+	return () => {
+		if (rafQueue.includes(fn)) {
+			return
+		}
+		rafQueue.push(fn)
+		raf()
+	}
+}
+
+/**
+ * Calls the function on the next frame.
+ * If the same fn is passed again before the next frame, it will still be called only once.
+ * @param fn - the fun to call on the next animation frame
+ * @returns
+ * @internal
+ */
+export function throttledRaf(fn: () => void) {
+	if (isTest()) {
+		return fn()
+	}
+
+	if (rafQueue.includes(fn)) {
+		return
+	}
+
+	rafQueue.push(fn)
+	raf()
+}