feat: per-message read receipt avatars showing each user s last-read position

src/app/features/room/ReadPositionsContext.ts

@@ -0,0 +1,4 @@
+import { createContext, useContext } from 'react';
+
+export const ReadPositionsContext = createContext<Map<string, string[]>>(new Map());
+export const useReadPositions = () => useContext(ReadPositionsContext);