Spaces: simple GPU instructions for PyTorch, JAX and tensorflow (#416)
* Simple GPU instructions: torch / JAX / tensorflow.
* Update overview to mention upgrades.
* Move GPU section before Gradio, as suggested in review.
* Add suggestions from code review.
* Add more detail and screenshots to `spaces-gpus`
* tweak
* consistency tweak
* Fix typo in path.
Co-authored-by: Julien Chaumond <julien@huggingface.co>