[Feature Request] Write tutorials as .py files

Motivation

Tutorials would benefit from being written in .py files, as they are in pytorch/tutorials.

The advantages are:

• fewer linting issues than .ipynb
• Fewer lines of code
• less issues with run/non-run cells
• better integration in doc

Solution

Torch uses notebook styled examples for this.

## Features

The new tutorials should match exactly the old ones in their content. They should appear in the doc in a dedicated section and they should have the colab / download / github banners like https://pytorch.org/tutorials/ have.