💡(frontend) document issue with the participant placeholder

It explains why participant initials doesn't update when a participant
changes its name.

Similar issue as the one faced while developing on the participant list.
It needs to be fixed at the root, in the LiveKit repo.

src/frontend/src/features/rooms/livekit/components/ParticipantPlaceholder.tsx

@@ -51,6 +51,7 @@ export const ParticipantPlaceholder = ({
           fontSize: `${initialSize}px`,
         }}
       >
+        {/*fixme - participant doesn't update on ParticipantNameChanged event */}
         <Avatar
           name={participant.name}
           bgColor={participantColor}