Add mlpack's ideas list.

Author: rcurtin

2025/ideas-list.md

@@ -11,6 +11,7 @@ page of each organization under the NumFOCUS umbrella at this page.
 - [Data Retriever](https://github.com/weecology/retriever/wiki/GSoC-2025-Project-Ideas)
 - [DISCOVER Cookbook](https://github.com/numfocus/DISCOVER-Cookbook/discussions/208)
 - [igraph](https://github.com/igraph/igraph/wiki/Mentored-Projects)
+- [mlpack](https://github.com/mlpack/mlpack/wiki/SummerOfCodeIdeas)
 - [NetworkX](https://networkx.org/documentation/latest/developer/projects.html)
 - [Open2C](https://github.com/open2c/open2c.github.io/wiki/GSoC-2025)
 - [optimagic](https://github.com/optimagic-dev/optimagic/discussions/559)