Add EclipticPlane

[paweel-srt]

Is your feature request related to a problem? Please describe.
For archaeoastronomy reasons, it would be nice to have the ability to plot a map of stars and constellations relative to the plane of the ecliptic, just like as GalaxyPlot do relative to galaxy ecuator

Describe the solution you'd like
Plot a sky map using ecliptic coordinate system with ecliptic line in the middle

Additional context

[steveberardi]

I'd love to add support for this, so I'll put it on the roadmap, but it may be awhile until I have time to work on this. I'm currently working on an SVG backend that'll dramatically improve performance and more.

Thanks for the idea!

Steve