Adds left and right panels

[JasonWeill]

Addreses #6326 by adding a left and right panel to Jupyter Notebook.

Adapted from jupyterlab/retrolab#275 which was to address jupyterlab/retrolab#272.

[github-actions]

👈 Launch a Binder on branch jweill-aws/notebook/left-right-widgets

[brichet]

Is there an update on this ?
Are any features missing ?

[jtpio]

I think one of the blockers was being able to reuse the table of contents extension from JupyterLab in Notebook v7.

It was not easily possible for a while but should be possible now with the latest JupyterLab 4.0.0ax pre-releases.

[jtpio]

It was not easily possible for a while but should be possible now with the latest JupyterLab 4.0.0ax pre-releases.

In particular jupyterlab/jupyterlab#12374 which was released in 4.0.0a25: https://github.com/jupyterlab/jupyterlab/releases/tag/v4.0.0a25.

[jtpio]

@jweill-aws were you planning to resume work on this branch?

[JasonWeill]

@jtpio I am actively working on a different project at the moment. I don't have a plan to resume work on this item in the near term.

[brichet]

Thanks for answering.
I'll take a look at it as soon as possible.

[brichet]

I rebased the PR and added the TOC dependency here.
The table of contents exists in left menu but is empty.

The widget is null after : https://github.com/jupyterlab/jupyterlab/blob/039934615eae2405f82a071152d8da8ee432727e/packages/toc-extension/src/index.ts#L274

It seems that the app.restored is resolved before the document is attached to the main area.

[jtpio]

Thanks @jweill-aws and @brichet.

I don't have a plan to resume work on this item in the near term.

@brichet maybe we can open a new PR based on this commit and continue there?

[brichet]

@brichet maybe we can open a new PR based on this commit and continue there?

I opened #6487