У вашего броузера проблема в совместимости с HTML5
New 2D skeletal deformation functionality was just released in the developer branch of Godot 3. Of course we show you how to use it in this step by step guide.
If you want to learn more be sure to check out the initital announcement at:
https://godotengine.org/article/godot-gets-2d-skeletal-deform