add studio (#75)

* add studio

* Update README.md

---------

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

Author: khlebobul

README.md

@@ -161,7 +161,7 @@ Tools to create vector artwork from scratch or by conversion from other formats.
 - [REVDANCATT Plotter Tools](https://revdancatt.com/penplotter/) - A bunch of web-based pen plotter tools with SVG output.
 - [Flow Lines](https://msurguy.github.io/flow-lines/) - A tool for generating flow line representations using SVG paths / polylines.
 - [UJI](https://doersino.github.io/uji/) - A web-based generative art thing with SVG export.
-
+- [Studio](https://u840903.github.io/multiplication-mandalas/) - A web-based tool for creating multiplication mandalas.
 
 ### Vector Utilities