Add xCDAT tutorial datasets and update gallery notebooks (#705)

Fix imports in test_tutorial.py

Update xcdat/tutorial.py

Fix spatial-average.ipynb rebase changes

Fix spatial-average.ipynb rebase changes

Update general-utilities.ipynb

Update date for hourly data

Add module level docstring

Update docs/getting-started-guide/installation.rst

Update hourly dataset in climatology-and-departures.ipynb

Add unit adjustment to tas in cwss notebook

Update CWSS introduction-to-xcdat.ipynb

Update introduction-to-xcdat.ipynb

Add pooch to ci.yml

Fix pre-commit warning

Add pooch to list of optional dependencies

Move pooch import to inside open_dataset() and add tests

Update temporal-average.ipynb and add tas_3hr_access

Update parallel-computing-with-dask.ipynb

Remove usage of xarray.tutorial_open_dataset()`

Remove usage of xarray.tutorial_open_dataset()`

Fix API docstring

Fix pre-commit issues

Update regridding-vertical.ipynb

Update regridding-horizontal.ipynb

Update spatial-average.ipynb

Update spatial_average.ipynb

Update htree notebooks

Add old notebooks back to edit with new tutorial datasets

Add new examples to new dir for temp storage