Node.js: response body chunk can now be a Uint8Array.

Starting from Node.js 15.0.0 the chunk parameter of the response.write()
can be a Uint8Array.

This closes #870 issue on GitHub.

test/test_node_application.py

@@ -149,6 +149,10 @@ def test_node_application_write_buffer():
 
     assert client.get()['body'] == 'buffer', 'write buffer'
 
+def test_node_application_write_array():
+    client.load('write_array')
+
+    assert client.get()['body'] == 'array', 'write array'
 
 def test_node_application_write_callback(temp_dir):
     client.load('write_callback')