Dark mode

[Fil]

Dark mode almost works: the use of currentColor for stroke and fill is solving 90% of the problem.

In some cases, though, it's not ideal:

• in cars-parcoords we use white to detach the text against the background. Using "fill: currentColor; filter: invert(1)" would work.
• in metroUnemploymentRidgeline the areas are filled with #ccc, which could be replaced by "fill: currentColor; filter: invert(20%);"
• and more.

Adding support for the filter attribute would help a lot.

See also #1461

[Fil]

A smaller issue is that hard-coded .plot background {#fff}, which I had to override in bf7b99f

[mbostock]

We support dark mode in our documentation and I even tweeted about it:

https://twitter.com/mbostock/status/1653069773645938689

Maybe we can close this issue? Maybe the last remaining issues are the default white background #1434 and the default white marker stroke #1463 but both issues can be worked around with a stylesheet.

[Fil]

At some point we'll have to consolidate the documentation, but in terms of support I think we have all we need.