adds download dataset to docs

Author: normanrz

docs/mkdocs.yml

@@ -73,6 +73,7 @@ nav:
       - Dataset Examples:
         - webknossos-py/examples/dataset_usage.md
         - webknossos-py/examples/upload_image_data.md
+        - webknossos-py/examples/download_image_data.md
       - webknossos-py/examples/apply_merger_mode.md
       - webknossos-py/examples/learned_segmenter.md
       - webknossos-py/examples/skeleton_synapse_candidates.md