fix middleware and command types

src/def/interfaces.ts

@@ -85,4 +85,6 @@ export interface CommandOptionConfig {
   config?: CommandOptionConfigWithDescription;
 }
 
-export type CommandReturnType = CanBeObserved<string | void | segment>;
+export type CommandReturnType = CanBeObserved<
+  string | void | segment | (string | segment)[]
+>;

src/utility/rxjs-session.ts

-import { Awaitable, Session, segment } from 'koishi';
+import { Awaitable, Session } from 'koishi';
 import { isObservable, Observable } from 'rxjs';
+import { CommandReturnType } from '../def';
 
 export type CanBeObserved<T> = Awaitable<T | Observable<T>>;
 
 export async function sessionRxToPromise(
   session: Session,
-  obs: CanBeObserved<string | void | segment>,
+  obs: CommandReturnType,
 ) {
   const obsAwaited = await obs;
   if (!isObservable(obsAwaited)) {