Update gitignore files and add JupyterLab3 keyword

[goanpeca]

Related to #106

[echarles]

LGTM. Thx @goanpeca

[jasongrout]

Following the pattern at https://github.com/pypa/trove-classifiers/blob/master/src/trove_classifiers/__init__.py#L105, should we do "Framework :: JupyterLab :: 3", or perhaps "Framework :: Jupyter :: JupyterLab :: 3"?

[goanpeca]

Sure why not, but what is optional and needs to exist? Or which one can we use right away?

[jasongrout]

Good question. I don't know if we can use classifiers that aren't officially listed. More about the application process over at #106 (comment) - I think this can probably be done in parallel with a keyword (in fact, having a keyword would make it easier to find packages that would be on the application for the trove classifier)

[goanpeca]

@jasongrout will work on requesting the trove classifier as you suggested on #106.

This one should be good to merge anyway while the other part is done. As you rightly pointed out,

having a keyword would make it easier to find packages that would be on the application for the trove classifier

So we can merge :)

Any takers to press the green button :-p ?

[echarles]

Thx @goanpeca Merged.