Feature: Implement rangefinder-like sensor that also returns the geom-id

[cowolff]

We need to be able to get more information out of the rangefinder sensor because by default it only returns the distance. But we also need to be able to retrieve additional information, like color and so on. To achieve this, we will have to implement our own rangefinder alternative that returns the id of the geom that the rangefinder is pointed at as well.
In this Github issue, they provide a nice and sleek implementation of that. We need to integrate that into our environment in an easy-to-use way. google-deepmind/mujoco#748