Update README.md with motheme (#2)

Author: akshayka

README.md

@@ -60,6 +60,7 @@ _Have a project or resource you'd like to add? Submit a [pull request](https://g
 
 ## Projects Using marimo
 
+- [motheme](https://github.com/metaboulie/marimo-themes) - Install custom themes for the marimo editor.
 - [marimo on mutable.ai](https://mutable.ai/marimo-team/marimo) - An AI-generated wiki of the marimo codebase, with chat support.
 - [marimo Guru](https://gurubase.io/g/marimo) - Chat with the marimo docs and codebase.