Thumbnail data should be in the form of a base64 string and also be used for display on the emoji panel to avoid wasting traffic caused by directly using the original image.
If the image resource is a GIF image and it is desired to send it in the form of a GIF message, then the GIF image information needs to be provided. Otherwise, it will be sent as a static image message by default.
[ZH] 网络资源托管地址, 如：https://xxxxx，地址需确保各端网络环境的可访问性