add contribute.md

Author: frankwhzhang

README.md

@@ -84,6 +84,7 @@ python -u tools/static_trainer.py -m models/rank/dnn/config.yaml #  静态图训
 * [分布式训练](doc/fleet_mode.md)
 
 ### 进阶教程
+* [提交规范](doc/contribute.md)
 * [自定义Reader](doc/custom_reader.md)
 * [自定义模型](doc/model_develop.md)
 * [yaml配置说明](doc/yaml.md)