[LINE] support 2018/11/08 change

[tw0517tw]

https://developers.line.me/en/news/#specification-change-for-the-messaging-api-2018-11-08

You can play videos in imagemap messages

Now you can play videos in imagemap messages.

For more information, see Imagemap message.

Note that this change doesn't include the validation of action areas of imagemap messages announced on October 24. We will inform you once we decide on our schedule.

Flex Messages can now be multicast

Now you can send Flex Messages with the /v2/bot/message/multicast endpoint.

For the /v2/bot/message/multicast endpoint, see Send multicast messages in the Messaging API reference.