Rm sphinx doc
Thanks for pushing this :)
One minor comment regarding the PR itself - I noticed that some changes are coming from the upstream master, this might be due to a rebase. Would be nice if this PR doesn't include them for readabily, feel free to open a new one if necessary Closing in favour https://github.com/huggingface/datasets/pull/3741
Checklist 
- [x] Update circle ci yaml
- [x] Delete sphinx static & python files in docs dir
- [x] Update readme in docs dir
- [ ] Update docs config in setup.py