[examples] adding the references for the new video API (#2770)

* gitignore now supports IPYNB aux files

* Adding the reference ipython notebook

* Update location

* link fix

* Add autodownload for colab

* rename and address fmassa's comments

* nitpicks

* nitpicks

* Apply suggestions from code review
Co-authored-by: Francisco Massa <fvsmassa@gmail.com>

.gitignore

@@ -23,3 +23,4 @@ gen.yml
 .mypy_cache
 .vscode/
 *.orig
+*-checkpoint.ipynb
\ No newline at end of file

examples/python/README.md

@@ -2,6 +2,9 @@
 
 - [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/pytorch/vision/blob/master/examples/python/tensor_transforms.ipynb)
 [Examples of Tensor Images transformations](https://github.com/pytorch/vision/blob/master/examples/python/tensor_transforms.ipynb)
+- [![Open In Colab](https://colab.research.google.com/assets/colab-badge.svg)](https://colab.research.google.com/github/pytorch/vision/blob/master/examples/python/video_api.ipynb)
+[Example of VideoAPI](https://github.com/pytorch/vision/blob/master/examples/python/video_api.ipynb)
+
 
 Prior to v0.8.0, transforms in torchvision have traditionally been PIL-centric and presented multiple limitations due to 
 that. Now, since v0.8.0, transforms implementations are Tensor and PIL compatible and we can achieve the following new 
@@ -11,3 +14,5 @@ features:
 - support for GPU acceleration
 - batched transformation such as for videos
 - read and decode data directly as torch tensor with torchscript support (for PNG and JPEG image formats)
+
+Furthermore, previously we used to provide a very high-level API for video decoding which left little control to the user. We're now expanding that API (and replacing it in the future) with a lower-level API that allows the user a frame-based access to a video.