cli: add support for the kitty graphics protocol

[sondove]

Ascii art is cool, but real charts in the terminal is even cooler. A lot of modern terminal emulators are coalescing around the kitty graphics protocol (after the terminal emulator) and it would be fun to support that out of the box.

This should be a fairly simple hack as the pngs are already rendered server side and we "just" have to get the dimensions, fetch the right image and output the correct control codes.

I suggest using -X uppercase X for this output, both for the ipython friendly plt.X and the cli.

[sondove]

We should of course make sure to only grab proper novem urls.

Here is a library that appears to implement the code (https://pypi.org/project/term-image/)