Fix downloading of lerobot dataset

[02alexander]

Fixes issue #2
Solution was found here https://huggingface.co/datasets/lerobot/pusht/discussions/2

[jleibs]

Is pip installing from the git url the right way to install? Is it not available as a pypi package?

[02alexander]

lerobot exists as a package on pypi, but it's one month old and it doesn't have lerobot.common.datasets.video_utils which we need.

[02alexander]

In the lerobot repository README they only mention installation via git, so I think that is the preferred option.

[02alexander]

I discovered another problem, right now we only get the path to the video + timestamp.

[02alexander]

@jleibs The lerobot datasets (version >= 1.2) are a bit complicated to download since the images are stored in a separate video files that needs to be downloaded, so I decided to let the lerobot package (via git) handle downloading of the dataset. One downside of doing it this way is that lerobot is a huge dependency, but now it should still work even if they update how the dataset is stored.