New repository: Next Generation Kernels API

[Zsailer]

For a while, I've been working on refactoring the Jupyter Server Kernels API.

https://github.com/Zsailer/nextgen-kernels-api

There are many reasons for this; however, the reason that is relevant to this organization/effort is to provide stable kernel message routing APIs for server-side document models.

I'd like to propose we move the nextgen-kernels-api into the jupyter-ai-contrib organization.

Some of this work has been forked in jupyter-server-documents already.

I've revived and published the nextgen-kernels-api repo to move this work out of jupyter-server-documents and into this repo until we're able to upstream these APIs into Jupyter Server. I am drafting a PR for jupyter-server-documents now that removes the forked APIs and depends on this package.

Separately, I'll start a conversation in jupyter-server repo to move these APIs into core.

In the meantime, having the repo in this organization enables us to use the releaser here and the collaborate more easily.

[Zsailer]

Opened a PR against jupyter-server-documents to use this new API: jupyter-ai-contrib/jupyter-server-documents#170