Add the readme file for the peft.

examples/singa_peft/README.md

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+
+# Singa PEFT
+
+## Code structure design
+
+The code structure design is shown in the following figure. For details, please refer to the next section, which will give a detailed explanation.
+
+<img alt="img.png" height="400" src="docs/peft.png" width="600"/>
+
+
+## Code structure specification
+
+The code structure is shown in the tree structure below, which is specified as follows:
+
+```
+_singa-peft/
+├── __init__.py
+├── tuner/                  
+│   ├── __init__.py
+│   ├── base_tuner.py       
+│   └── linear_lora/        
+│       ├── __init__.py
+│       ├── config.py       
+│       ├── layer.py        
+│       └── tuner.py       
+├── peft_config.py         
+├── peft_registry.py             
+└── peft_model.py          
+``` 
+
+`peft_config.py` contains the peft configuration base class **PeftConfig**, which defines some common parameters. All other peft configuration classes must inherit from this class.
+
+
+`peft_registry.py` contains the **PeftRegistry** class. You can register a new peft tuner by using the annotation `@PeftRegistry.register("xxx")`.
+
+
+`base_tuner.py` contains the **BaseTuner** class, which is the base class for all tuners. All peft methods must inherit from this class and implement `inject` and `merge_weights` abstract methods.
+
+
+`linear_lora/config.py` contains **LinearLoraConfig** class, and inherits from **PeftConfig** class, which includes the necessary parameters for lora method.
+
+
+`linear_lora/layer.py` contains the **LinearLoRALayer** class, which is the implementation of the Lora method in a linear layer. The tuner's `inject` method replaces the linear layer in the base model with this layer.
+
+
+`linear_lora/tuner.py` contains **LinearLoraTuner** class, which inherits from **BaseTuner** class. First you need to register the peft method with the annotation `@PeftRegistry.register("linear_lora")` on the class. Next, you need to implement abstract methods that inherit from **BaseTuner**, including `inject` and `merge_weights` abstraction methods. The `inject` method implementation specifies the layers to replace, for example, the normal `linear layer` instead of the `linearLora layer`. The `merge_weights` method merges the parameters of the replaced layers to speed up the inference.
+
+
+Finally, if you want to extend the new peft method, you can follow the script in the `linear_lora` directory. In addition, you need to expose the corresponding classes and methods in the `__init__.py` file. Also see the scripts in the `examples` directory for how to use the library.