Fixed script to output the JSON and create doc directory.

components/style/list_properties.py

@@ -23,12 +23,17 @@
 )
 
 json_dump = json.dumps(properties, indent=4)
+print(json_dump)
 
 #
 # Resolve path to doc directory and write CSS properties and JSON.
 #
 servo_doc_path = os.path.abspath(os.path.join(style, '../', '../', 'target', 'doc', 'servo'))
 
+# Ensure ./target/doc/servo exists
+if not os.path.exists(servo_doc_path):
+    os.makedirs(servo_doc_path)
+
 with open(os.path.join(servo_doc_path, 'css-properties.json'), "w") as out_file:
     out_file.write(json_dump)