- Updated `lerobot_dataset.py:add_frame` to take task as key in frame
- Updated `lerobot_dataset.py` to remove robot argument from `create` function of lerobotdataset and lerobotdatasetmetadata and directly take the features
- Update `test_datasets.py` to features from Mock robot
- Update all the usage of `add_frame` in the library
- Update `dataset_factories.py`; had issues with new argument order
- Raise ValueError when no task is provided (in `datasets/utils.py` validate func)