Make it possible to use the decorator @TelegramActionHandler without message

[evilsprut]

This code doesn't work:

@TelegramActionHandler({ message: '' })

[edgesite]

The empty string is false value so handlers.filter(({ config }) => config.message) filtered out {message: ''}. Use following code instead of
https://github.com/bukhalo/nestjs-telegraf/blob/cef3796f01c5086f6e8438876de5e828056c8056/lib/telegraf.service.ts#L99 may solve that:

private setupOnMessage(handlers: Handler[]): void {
    const onMessageHandlers = handlers.filter(({ config }) => config.message !== undefined)

    onMessageHandlers.forEach(handler => {
      if (handler.config.message) {
        this.bot.hears(handler.config.message, this.adoptHandle(handler))
      } else {
        this.bot.on('message', this.adoptHandle(handler);
      }
    });
  }

[evilsprut]

@all-contributors please add @edgesite for code, bug

[allcontributors]

@bukhalo

I've put up a pull request to add @edgesite! 🎉