Add a json editor

[jasongrout]

This looks promising: https://github.com/josdejong/jsoneditor

[eskirk]

@jasongrout I'm gunna check this out, seems simple enough
the only thing is, the typed file seems outdated (https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/jsoneditoronline/jsoneditoronline.d.ts).
Should it still work even though the repo has been renamed/moved?

[jasongrout]

I'm not sure if the typing file still works, though it shouldn't depend on the repo location.

I'd say this is probably lower priority than #472, though.

[xtrntr]

This looks interesting, but i'm not quite entirely sure how and where a JSON editor is going to fit in.

[jasongrout]

I think @gnestor worked on this. Grant, can you comment?

[gnestor]

https://github.com/jupyterlab/jupyterlab_json is currently working for viewing JSON (not editing). I've managed to integrate https://github.com/gnestor/notebook_json into the same Python package, so after I publish to PyPI, a user should be able to pip install jupyterlab_json (or pip install jupyter_json?) and install extensionsfor both notebook and lab. I like the idea of a JSON editor but I'd like to hear more about how it might be used vs. using a text editor.

[cocoaaa]

Currently, it seems .geojson files are not recognized as json-like format in the editor. It would be nice if the editor does so:

[gnestor]

Good catch @cocoaaa! It's an easy fix. I'll submit a PR 👍

[gnestor]

#6349