add crop notebook

_toc.yml

@@ -6,6 +6,7 @@
 - part: Tutorials
   chapters:
     - file: docs/Quick_start
+    - file: docs/Crop_data
         
 - part: The xarray dependencies
   chapters:

environment.yml

@@ -10,6 +10,7 @@ dependencies:
   - xarray
   - scikit-learn
   - scikit-image
+  - ipywidgets
   - pip
   - pip:
     - -e git+https://github.com/ThomasChauve/xarray_uvecs.git@main#egg=xarrayuvecs