Hi! I've added GIFs into my signature before, so I can help you out!
First, open the GIF image in a new tab, then copy the URL of the image into your signature. Be sure to add in the URL in the image tab of the message box (between the link and emoji icons).
First, open the GIF image in a new tab, then copy the URL of the image into your signature. Be sure to add in the URL in the image tab of the message box (between the link and emoji icons).
The URL of your image is this: https://i.giphy.com/qkUMU1ZUnPrFe.webp
So, I put the URL in the "image" tab and this appears!