message: fix(types): fix vm.$once argument type
  vm.$once should accept an event or array of events as first parameter.
  fix
diff: @@ -53,7 +53,7 @@ export interface Vue {
  options?: WatchOptions
  ): (() => void);
  $on(event: string | string[], callback: Function): this;
  - $once(event: string, callback: Function): this;
  + $once(event: string | string[], callback: Function): this;
  $off(event?: string | string[], callback?: Function): this;
  $emit(event: string, ...args: any[]): this;
  $nextTick(callback: (this: this) => void): void;
  