Get content transcoding status and a preview image

[YasSawada]

News URL https://developers.line.biz/en/news/2023/02/14/messaging-api-updated/

• Endpoint to verify the preparation status of a video or audio for getting
• Endpoint to get a preview image of an image or video

[moririnson]

It supported by https://github.com/line/line-bot-sdk-php/releases/tag/8.0.0 .