chore: Editor 'plugin' -> 'extension'

They've always been called extensions, not sure why the folder was plugins. Part of ongoing spring cleaning

app/scenes/Document/components/MultiplayerEditor.tsx

@@ -5,6 +5,7 @@ import { useTranslation } from "react-i18next";
 import { useHistory } from "react-router-dom";
 import { IndexeddbPersistence } from "y-indexeddb";
 import * as Y from "yjs";
+import MultiplayerExtension from "@shared/editor/extensions/Multiplayer";
 import Editor, { Props as EditorProps } from "~/components/Editor";
 import env from "~/env";
 import useCurrentToken from "~/hooks/useCurrentToken";
@@ -14,7 +15,6 @@ import useIsMounted from "~/hooks/useIsMounted";
 import usePageVisibility from "~/hooks/usePageVisibility";
 import useStores from "~/hooks/useStores";
 import useToasts from "~/hooks/useToasts";
-import MultiplayerExtension from "~/multiplayer/MultiplayerExtension";
 import Logger from "~/utils/Logger";
 import { supportsPassiveListener } from "~/utils/browser";
 import { homePath } from "~/utils/routeHelpers";