updated README.md

## algorithm description

The `csst_proto` uses an awesome algorithm based on `numpy.ndarray` indices to flip images.

## timeline

| file / directory   | description                     | notes | C6  | C7  |

|--------------------|---------------------------------|-------|-----|-----|

| `csst_proto`       | source code & data              |       | √   |     |

| `doc`              | sphinx-based documentation      |       |     | √   |

| `example`          | code examples                   |       | -   | -   |

| `tests`            | unit tests                      |       |     | √   |

| `.gitignore`       | git file                        |       | √   |     |

| `.gitlab-ci.yml`   | gitlab CI/CD pipeline           |       |     | √   |

| `LICENSE`          | code license                    |       | √   |     |

| `README.md`        | readme file                     |       | √   |     |

| `install.sh`       | single-line installation script |       | √   |     |

| `install_local.sh` | local installation script       |       | √   |     |

| `readthedocs.yml`  | readthedocs.io configuration    |       |     | √   |

| `requirements.txt` | code requirements               |       | √   |     |

| `setup.py`         | sphinx-based documentation      |       | √   |     |

## 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