docs: update theming guide with community contributions

docs/guides/configuration/theming.md

@@ -85,15 +85,13 @@ You can target a cell's styles from the `data-cell-name` attribute. You can also
 
 ## Community Themes
 
-The marimo community maintains a [library of custom themes](https://github.com/metaboulie/marimo-themes) that you can use in your notebooks. The library includes various themes like "coldme", "nord", "mininini", and "wigwam", each supporting both light and dark modes.
+!!! tip "Community Contributions"
 
-You can:
-
-- Browse and download existing themes
-- Use them in your own notebooks
-- Contribute your own themes to share with the community
-
-Visit the [marimo-themes repository](https://github.com/metaboulie/marimo-themes) to explore available themes and learn how to contribute your own.
+    The marimo community creates and shares custom themes. Here's an example to get you started:
+
+    **Christmas Theme**: [View on GitHub Gist](https://gist.github.com/Light2Dark/7d192d7f78906812682fe499314c4ada)
+
+    Share your own themes as GitHub Gists, or let us know if you'd like a community-driven theme repository.
 
 ## More customizations