Bootstrap structure for a widget examples repo

[jtpio]

First step towards a "Widget Examples" repository for ipywidgets: jupyter-widgets/ipywidgets#3136

Heavily inspired by the JupyterLab Extension Examples: https://github.com/jupyterlab/extension-examples

The idea is to set up the basic structure for multiple custom widget examples in the same repo, so that we have the tools and CI in place to iterate and easily add new examples.

TODO

• Set up the structure and tooling
• Add dev instructions to work on the repo
• Add hello-world example bootstrapped from the TS cookiecutter: https://github.com/jupyter-widgets/widget-ts-cookiecutter
• Make sure CI passes

[jtpio]

Example CI run in the fork: jtpio#1

[jtpio]

Seeing some ESOCKETTIMEDOUT on macos-latest:

https://github.com/jtpio/custom-ipywidget-howto/pull/1/checks?check_run_id=2120510605

Maybe we can keep ubuntu-latest on CI for now and add back macos and windows later on.

[jtpio]

Listing a couple of items to iterate on in follow-up PRs:

• Enable tests on CI with pytest
• Test on macos and windows on CI
• Add the existing two examples jslink-custom-widgets and connecting-widgets to the list of examples

[jtpio]

cc @ianhi if you want to have a look.

This PR is mostly about adding the tooling and the structure, more than actually working on the examples themselves.

Maybe there could be a couple more iterations before renaming the repo to widget-examples and moving it to the jupyter-widgets organization on GitHub.

[ianhi]

Hi @jtpio thanks so much for starting on this! I've been busy at the start of this week but will look at this tomorrow (today now?) evening.

[ianhi]

I had been playing a bit fast and loose with some of the formatting which prettier then mangled. So I updated that and removed some outdated portions of the readme.

[ianhi]

@jtpio do you know the answer to this?

[ianhi]

Suggested change

	This example was bootstrapped from the [Jupyter TypeScript Cookiecutter](https://github.com/jupyter-widgets/widget-ts-cookiecutter) and follows the same structure.
	This example was bootstrapped from the [Jupyter Widget TypeScript Cookiecutter](https://github.com/jupyter-widgets/widget-ts-cookiecutter) and follows the same structure.

Is that a more correct phrasing?

[ianhi]

This is fantastic. Thanks so much for this. I have some follow up questions about how to best improve this but they can go into new issues.