create prenotify types

apps/app/src/server/service/preNotify.ts

@@ -0,0 +1,7 @@
+import type { IUser } from '@growi/core';
+
+type PreNotifyProps = {
+  notificationTargetUsers?: IUser[],
+}
+
+export type PreNotify = (props: PreNotifyProps) => Promise<void>;