[Doc] add readme for js packages (#421)

* add contributor

* add package readme

* refine ocr readme

* refine ocr readme

examples/application/js/package/packages/paddlejs-models/facedetect/README.md

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+[中文版](./README_cn.md)
+
+# Facedetect
+
+Facedetect is used for face detection in image. It provides a simple interface. At the same time, you can use your own model.
+
+<img src="https://img.shields.io/npm/v/@paddle-js-models/facedetect?color=success" alt="version"> <img src="https://img.shields.io/bundlephobia/min/@paddle-js-models/facedetect" alt="size"> <img src="https://img.shields.io/npm/dm/@paddle-js-models/facedetect?color=orange" alt="downloads"> <img src="https://img.shields.io/npm/dt/@paddle-js-models/facedetect" alt="downloads">
+
+# Usage
+
+```js
+import { FaceDetector } from '@paddle-js-models/facedetect';
+
+const faceDetector = new FaceDetector();
+await faceDetector.init();
+// Required parameter：imgEle(HTMLImageElement)
+// Optional parameter: shrink, threshold
+// Result is face area information. It includes left, top, width, height, confidence
+const res = await faceDetector.detect(
+    imgEle,
+    { shrink: 0.4, threshold: 0.6 }
+);
+```
+
+# Performance
++ **multi small-sized face**  
+  <img width="500"  src="https://mms-voice-fe.cdn.bcebos.com/pdmodel/face/detection/pic/small.png"/>
+
++ **single big-sized face**  
+  <img width="500"  src="https://mms-voice-fe.cdn.bcebos.com/pdmodel/face/detection/pic/big.png"/>
+
+# Postprocess
+This model has a better recognition effect for small-sized faces, and the image will be shrink before prediction, so it is necessary to transform the prediction output data.  
+<img width="500"  src="https://mms-voice-fe.cdn.bcebos.com/pdmodel/face/detection/pic/example.png"/>  
+The red line indicates the predicted output result, and the green line indicates the converted result. dx dy fw fh are known parameters.
+
+# Reference
+[original model link](https://github.com/PaddlePaddle/PaddleHub/tree/release/v2.2/modules/image/face_detection/pyramidbox_lite_mobile)

examples/application/js/package/packages/paddlejs-models/facedetect/README_cn.md

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+[English](./README.md)
+
+# Facedetect
+
+Facedetect 实现图像中的人脸检测，提供的接口简单，支持用户传入模型。
+
+<img src="https://img.shields.io/npm/v/@paddle-js-models/facedetect?color=success" alt="version"> <img src="https://img.shields.io/bundlephobia/min/@paddle-js-models/facedetect" alt="size"> <img src="https://img.shields.io/npm/dm/@paddle-js-models/facedetect?color=orange" alt="downloads"> <img src="https://img.shields.io/npm/dt/@paddle-js-models/facedetect" alt="downloads">
+
+# 使用
+
+```js
+import { FaceDetector } from '@paddle-js-models/facedetect';
+
+const faceDetector = new FaceDetector();
+await faceDetector.init();
+// 使用时必传图像元素（HTMLImageElement），支持指定图片缩小比例（shrink）、置信阈值（threshold）
+// 结果为人脸区域信息，包括：左侧 left，上部 top，区域宽 width，区域高 height，置信度 confidence
+const res = await faceDetector.detect(
+    imgEle,
+    { shrink: 0.4, threshold: 0.6 }
+);
+```
+
+# 效果
++ **多个小尺寸人脸**  
+  <img width="500"  src="https://mms-voice-fe.cdn.bcebos.com/pdmodel/face/detection/pic/small.png"/>
+
++ **单个大尺寸人脸**  
+  <img width="500"  src="https://mms-voice-fe.cdn.bcebos.com/pdmodel/face/detection/pic/big.png"/>
+
+# 数据后处理
+此人脸检测模型对小尺寸人脸具有更好的识别效果，图像在预测前会进行缩小，因此需要对预测输出数据进行变换，及为**数据后处理过程**。示意如下：  
+<img width="500"  src="https://mms-voice-fe.cdn.bcebos.com/pdmodel/face/detection/pic/example.png"/>  
+红线标识的是预测输出结果，绿线标识的是经过转换后的结果，二者变换过程所涉及到的 dx dy fw fh均为已知量。
+
+# 参考
+[源模型链接](https://github.com/PaddlePaddle/PaddleHub/tree/release/v2.2/modules/image/face_detection/pyramidbox_lite_mobile)