add an art installation to Inspiration section (#36)

* add an art installation in Inspiration section

I saw a very cool art installation using a plotter last year and always give it as an example to my students. I thought it had its place in this list, go check it out ! :)
It uses topographic data from Mars to draw surface projections with a plotter, while giving info about data travel.
I put it in the Inspiration section, and added the subtitle in the link text for more clarity, I don't know if that fits your publishing standards
Thanks to all contributors for this awesome list ;)

* Update README.md

Co-authored-by: Brian Boucheron <brian@boucheron.org>

README.md

@@ -188,6 +188,7 @@ Blog posts, articles, tutorials, galleries, videos, et cetera.
 - [The Best XY Plotters in 2020](https://all3dp.com/2/pen-plotters-best-xy-plotters/) - Good overview of the AxiDraw and its clones, plus some DIY options.
 - [What is a pen plotter 2022?](https://www.youtube.com/watch?v=J1NpYzETm3M) - Nice video introduction to modern plotters in 2022.
 - [Tools, Tricks, and Hacks: Exploring Novel Digital Fabrication Workflows on #PlotterTwitter](https://dl.acm.org/doi/abs/10.1145/3411764.3445653) - Research paper on the novel workflows of the plotter community ([Video Summary](https://www.youtube.com/watch?v=xqhT-8ElJ68)).
+- [Orbis Tertius](https://www.glkitty.com/pages/orbistertius.html) - An immersive digital installation with plotter output of Martian topography.
 
 ## Manuals and Ephemera