Add todo

Author: VeckoTheGecko

workshops/scipy2026/index.ipynb

@@ -52,7 +52,7 @@
     "| *10 minute Break* \n",
     "| Xarray backends | 2:40 (60 min) | [Add link Intro to backends](../../advanced/backends/intro-backends.ipynb)|\n",
     "|||Working with Xarray's backends ([Zarr stores in the cloud](../../intermediate/hierarchical_zarr_store.ipynb), [Rioxarray](../../advanced/backends/rasterio_backend.ipynb) )|\n",
-    "|||Creating custom backends|\n",
+    "||| [TODO add link: Creating custom backends]() |\n",
     "| *10 minute Break* \n",
     "| Data cataloguing | 3:50 (40 min) | [Data cataloging](../../intermediate/cataloging.ipynb) |\n",
     "| *10 minute Break* \n",