add new notebook to toc

Author: scottyhq

_toc.yml

@@ -42,6 +42,7 @@ parts:
         sections:
           - file: intermediate/indexing/advanced-indexing.ipynb
           - file: intermediate/indexing/boolean-masking-indexing.ipynb
+      - file: intermediate/hierarchical_computation.ipynb
       - file: intermediate/xarray_and_dask
       - file: intermediate/xarray_ecosystem
       - file: intermediate/hvplot