Hide existing messages from ignored users (#2236)

* add ignored users hook

* remove messages from timeline for ignored users

src/app/hooks/useIgnoredUsers.ts

@@ -0,0 +1,18 @@
+import { useMemo } from 'react';
+import { useAccountData } from './useAccountData';
+import { AccountDataEvent } from '../../types/matrix/accountData';
+
+export type IgnoredUserListContent = {
+  ignored_users?: Record<string, object>;
+};
+
+export const useIgnoredUsers = (): string[] => {
+  const ignoredUserListEvt = useAccountData(AccountDataEvent.IgnoredUserList);
+  const ignoredUsers = useMemo(() => {
+    const ignoredUsersRecord =
+      ignoredUserListEvt?.getContent<IgnoredUserListContent>().ignored_users ?? {};
+    return Object.keys(ignoredUsersRecord);
+  }, [ignoredUserListEvt]);
+
+  return ignoredUsers;
+};