added standards.md

standards.md

+## CSST L1 Pipeline Standards
+
+### Workplace
+
+Gitlab Group **CSST-L1**:
+https://csst-tb.bao.ac.cn/code/csst-l1
+
+### Prototype
+
+https://csst-tb.bao.ac.cn/code/csst-l1/csst_proto
+
+### Structure of files
+
+An example of the tree
+
+```bash
+csst_proto
+ |-csst_proto
+ |  |-data
+ |  |  |-test_image.txt
+ |  |  |-table_data.txt
+ |  |-__init__.py
+ |  |-flip_image.py
+ |  |-some_other_modules.py
+ |  |-top_level_interface.py
+ |-tests
+ |-doc (sphinx directory)
+ |-setup.py
+ |-LICENSE
+ |-README.md
+```
+
+
+1. `setup.py`
+    this file 
+
+2.
+
+### Code style
+
+PEP8.
+
+### Documentation
+
+sphinx-based documentation needs docstrings.
+
+1. docstring styles
+    - Numpy (recommended)
+    - Google
+
+### Unit Tests
+
+