message: fix async BTD msg listener
diff: @@ -31,7 +31,7 @@ export function isMessageEventAllowed(ev: MessageEvent) {
  export type BTDMessageEventHandler = (
  ev: BTDMessageEvent
  -) => BTDMessageEventData | void | never | Promise<any>;
  +) => BTDMessageEventData | void | Promise<void> | Promise<BTDMessageEventData>;
  export function listenToInternalBTDMessage(
  name: BTDMessages,
  @@ -39,7 +39,7 @@ export function listenToInternalBTDMessage(
  location: BTDMessageOriginsEnum,
  handler: BTDMessageEventHandler
  ) {
  - const listener = (ev: MessageEvent) => {
  + const listener = async (ev: MessageEvent) => {
  if (!isMessageEventAllowed(ev)) {
  return;
  }
  @@ -62,7 +62,7 @@ export function listenToInternalBTDMessage(
  return;
  }
  - const replyEvent = handler(ev);
  + const replyEvent = await handler(ev);
  if (!replyEvent) {
  return;
  