I was not able to find any mention of bezier curve collisions both in the roadmap and the general issue baclog on github.
You can use
Curve2D and tessellate it. Then generate
ConcavePolygonShape2D on runtime. This is not very efficient, and I guess not what you was looking for. You can also try to roll this on your own, like in the following example.
On the other hand, I see no reason why you can not suggest this as a feature. Simply open an issue on github.