Drop empty toctree glob in examples/index.md

Author: timtreis

examples/index.md

@@ -4,9 +4,8 @@ Short, focused notebooks demonstrating individual `spatialdata-plot` features.
 Use these as a quick reference when you know what you want to do and need to
 see the call shape.
 
-```{toctree}
-:maxdepth: 2
-:glob:
-
-*/index
+```{note}
+No examples yet — contributions welcome! See
+[CONTRIBUTING](https://github.com/scverse/spatialdata-plot-notebooks/blob/main/CONTRIBUTING.md)
+for how to add one.
 ```