CSV/JSON renderer in JupyterLab

[timkpaine]

Initial cut at a CSV/JSON viewer in jupyterlab

Standalone CSV/JSON viewer:

• Can parse records-oriented JSON or CVS, available from the right click menus for Open With
• Shows error for datatypes can't parse
• Grabs light/dark theme from environment
• Changes when theme is changed

Updates for PerspectiveWidget:

• If you don't pass in dark=True or dark=False, it will pick it up from the environment

[timkpaine]

[texodus]

Thanks for the PR and review! This is a cool feature!

I will merge this now, but I have reservations about this design. I do not think dark keyword argument is the right API for this, and I definitely do not think it belongs on PerspectiveViewer class. IMO, dark is Jupyter-specific and should be implemented as Widget.addClass() calls here where we already know the jupyter dark class names, rather than manipulating an attribute dark that ultimately does the same thing.

PerspectiveViewer inherits from Widget which makes this possible, as <perspective-viewer> inherits HTMLElement, and should similarly use class to manipulate DOM style.

[timkpaine]

Yep, I think we want to expose full styles themselves into python rather than just light/dark . But light/dark was an existing api, not a new api, so it wouldn't make sense to implement that change in this PR.