GitLab

Summary:
* Introduce the mini-index at `torchaudio.pipelines` page.
* Add introductions
* Update pipeline tutorials

https://output.circle-artifacts.com/output/job/ccc57d95-1930-45c9-b967-c8d477d35f29/artifacts/0/docs/pipelines.html

<img width="1163" alt="Screen Shot 2022-09-20 at 1 23 29 PM" src="https://user-images.githubusercontent.com/855818/191167049-98324e93-2e16-41db-8538-3b5b54eb8224.png">

<img width="1115" alt="Screen Shot 2022-09-20 at 1 23 49 PM" src="https://user-images.githubusercontent.com/855818/191167071-4770f594-2540-43a4-a01c-e983bf59220f.png">

https://output.circle-artifacts.com/output/job/ccc57d95-1930-45c9-b967-c8d477d35f29/artifacts/0/docs/generated/torchaudio.pipelines.RNNTBundle.html#torchaudio.pipelines.RNNTBundle

<img width="1108" alt="Screen Shot 2022-09-20 at 1 24 18 PM" src="https://user-images.githubusercontent.com/855818/191167123-51b33a5f-c30c-46bc-b002-b05d2d0d27b7.png">

Pull Request resolved: https://github.com/pytorch/audio/pull/2689

Reviewed By: carolineechen

Differential Revision: D39691253

Pulled By: mthrok

fbshipit-source-id: ddf5fdadb0b64cf2867b6271ba53e8e8c0fa7e49

Summary:
Pull Request resolved: https://github.com/pytorch/audio/pull/2096

run: `arc lint --apply-patches --paths-cmd 'hg files -I "./**/*.py"'`

Reviewed By: mthrok

Differential Revision: D33297351

fbshipit-source-id: 7bf5956edf0717c5ca90219f72414ff4eeaf5aa8

* Refactor tutorial organization

* Merge tutorial subdirectoris under to examples/gallery/tutorials
* Do not use index.rst generated by Sphinx-gallery
* Instead use flat structure so that all the tutorials are listed in left menu
* Use `_assets` dir for artifacts of tutorials

It turned out that generated tutorials can embed the audio if the following conditions are met.
This commit changes how audio samples are shown in tutorials so that they become playable in doc.

1. There is only one `IPython.display.Audio` call in a cell
2. An object of `IPython.display.Audio` is the last object interpreter receives in the cell
3. Audio format is `wav`
   (`flac` can be embedded as well, but browsers (Chrome/Safari) won't play it)

Ref: https://stackoverflow.com/a/33109647