[Feature Request] Add linear interpolation to FrameSkipTransform

Motivation

I would suggest adding an option for linear interpolation to the FrameSkipTransform (documentation here). This means, instead of repeating the same action frame_skip number of times for each step in the environment, we could instead keep track of action from the previous step and then interpolate towards the new action over frame_skip steps.

This means that at the first step, the previous action would be executed, at the final step, the new action would be executed, and in between, we interpolate linearly between the two actions.

Solution

Add a variant of the FrameSkipTransform, or otherwise add this as an option in the params of FrameSkipTransform.

Checklist

• I have checked that there is no similar issue in the repo (required)