Add link to video dataset
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7277). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.
This PR updates https://huggingface.co/docs/datasets/loading to also link to the new video loading docs.

cc @mfarre 