[CORL-391] Fix jankiness when opening reply box of last comment in Stream (#2447)

* feat: add useResizeObserver hook

* fix: stream jumps when clicking on the last reply button when scrolled to the bottom

* chore: use resize observer in auth popup and simplify resize handling

* fix: snapshots and remove resize observer from stream

* fix: focus unmounted rte

src/core/client/framework/hooks/index.ts

@@ -3,3 +3,4 @@ export { default as usePrevious } from "./usePrevious";
 export { default as useEffectWhenChanged } from "./useEffectWhenChanged";
 export { default as useUUID } from "./useUUID";
 export { default as useToken } from "./useToken";
+export { default as useResizeObserver } from "./useResizeObserver";

src/core/client/framework/hooks/useResizeObserver.ts

@@ -0,0 +1,28 @@
+import { useEffect, useRef } from "react";
+import ResizeObserver from "resize-observer-polyfill";
+
+export default function useResizeObserver(
+  cb: (entry: ResizeObserverEntry) => void
+) {
+  const ref = useRef<any>(null);
+  useEffect(() => {
+    const element = ref.current;
+    if (element) {
+      const resizeObserver = new ResizeObserver(entries => {
+        if (!Array.isArray(entries)) {
+          return;
+        }
+        if (entries.length === 0) {
+          return;
+        }
+        // We are only observing one element.
+        const entry = entries[0];
+        cb(entry);
+      });
+      resizeObserver.observe(element);
+      return () => resizeObserver.unobserve(element);
+    }
+    return;
+  }, [ref.current]);
+  return ref;
+}