Add some jupyter examples to the docs

[manthey]

We probably want two sets of jupyter examples showing off some of the convenience functions, one without girder and one with.

The one without girder would show off some convenience methods:

!pip install large_image[sources] --find-links=https://girder.github.io/large_image_wheels
!curl "https://data.kitware.com/api/v1/file/5fdcf3dd2fa25629b99e0a9e/download" -o sample.svs
import large_image
ts = large_image.open('sample.svs')
ts
ts.metadata
ts.getThumbnail()[0]
large_image.tilesource.jupyter.IPyLeafletMixin.JUPYTER_PROXY = True
ts

And one with girder:

import girder_client, large_image, numpy as np, pickle
gc = girder_client.GirderClient(apiUrl='https://<server>/api/v1')
resource = '/collection/TCGA/single/TCGA-DX-A6BG-01Z-00-DX2.34763958-0613-4069-9ACC-13D6633FE415.svs'
itemId = gc.get('resource/lookup', parameters={'path': resource})['_id']
metadata = gc.get(f'item/{itemId}/tiles')
metadata
tileUrl = gc.urlBase + f'item/{itemId}/tiles' + '/zxy/{z}/{x}/{y}'
regionUrl = gc.urlBase + f'item/{itemId}/tiles/region?encoding=pickle'
thumbUrl = gc.urlBase + f'item/{itemId}/tiles/thumbnail?encoding=pickle'
pickle.loads(requests.get(thumbUrl).content)
# TODO: get thumbnail image, get actual region, show ipyleaflet layer

We can't use colab to render the first item fully, since the proxy doesn't work in colab.

[manthey]

Added in #1281.