And if you want to keep your current Dockerfile in the root directory, make a directory called binder there and put the Dockerfile that Binder will specifically use there in that binder directory.
However, your current Dockerfile looks very minimal, you could probably just use an environment.yml file in your binder directory and accomplish the same thing more easily and have something that will build faster & more easily on MyBinder, see here. If you go that way, move your stuff from requirements.txt under pip in the new environment.yml. The use of Dockerfile is best reserved for the more trickier builds, see here. Granted, I only glanced cursorily at your repo and I may have missed some complexity that rules this out.