I want to add video-icon class in dot if the gallery has video.
One way would be with JS, by targeting the Video frame that is active, in order to find the dot that is active at the same time.
Fotorama video class: "fotorama__stage__frame fotorama-video-container ... fotorama__active ..."
Dot active class: "fotorama__nav__frame fotorama__nav__frame--dot fotorama__active"
Then customize that specific dot (add a class, add icon, etc).