Our current thinking is that we aren't going to offer video/gifs for now (potentially ever) because there are already companies like Loom that do it so amazingly well.
We would rather be great at one thing (screenshots/all non video file annotations) rather than mediocre at two things. We think there is a lot to be done in the space we're currently in and that our assessment from talking to users is that having two tools for these two needs is ok.
That said, it may prove to be a necessity and if so we'll do it. But we are being disciplined here as a product lead and don't want to head down that path until we feel it's necessary and where we can provide a product that meets 80% of the use cases.
We wrote a blog post with more detail on this here: https://markuphero.com/blog/why-markup-hero-doesnt-offer-video/