You can apply it yourself 
I don’t think we’re on the same page. In the video you provided in the original post, you showcased the issue on a third person character, which I assume is the player character in your game. And IK feet are usually not a part of first person games. Could you clarify what’s going on?
While not being sure, I feel like you also want to be able to have this feature in the first person mode. There shouldn’t be any difference in the IK feet logic, but here’s a tutorial on switching between third person and first person:
Hope this helps! 