feat: Show collab cursor names upon loading document. (#2732)

Second attempt, adds a class to the editor for a couple of seconds when the awareness is loaded to force cursors to display

app/hooks/useIsMounted.js

@@ -0,0 +1,21 @@
+// @flow
+import * as React from "react";
+
+/**
+ * Hook to check if component is still mounted
+ *
+ * @returns {boolean} true if the component is mounted, false otherwise
+ */
+export default function useIsMounted() {
+  const isMounted = React.useRef(false);
+
+  React.useEffect(() => {
+    isMounted.current = true;
+
+    return () => {
+      isMounted.current = false;
+    };
+  }, []);
+
+  return React.useCallback(() => isMounted.current, []);
+}