add extend array to writing tutorial

Author: dylanmcreynolds

docs/source/tutorials/writing.md

@@ -60,6 +60,20 @@ Write array and tabular data.
 >>> client.write_array(numpy.array([4, 5, 6]), metadata={"color": "blue", "barcode": 11})
 <ArrayClient shape=(3,) chunks=((3,),) dtype=int64>
 
+# Create an array and grow it by one
+>>> new_array = client.write_array([1, 2, 3])
+>>> new_array
+<ArrayClient shape=(3,) chunks=((3,),) dtype=int64>
+
+# Extend the array. This array has only one dimension, here we extend by one 
+# along that dimension.
+>>> new_array.patch([4], offset=(3,), extend=True)
+>>> new_array
+<ArrayClient shape=(4,) chunks=((3, 1),) dtype=int64>
+>>> new_array.read()
+array([1, 2, 3, 4])
+>>> 
+
 # Write a table (DataFrame).
 >>> import pandas
 >>> client.write_dataframe(pandas.DataFrame({"x": [1, 2, 3], "y": [4, 5, 6]}), metadata={"color": "green", "barcode": 12})