Initial the documentation (#1)

* Disable npm package lock

* Initial the documentation

.npmrc

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+package-lock=false

README.md

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 [![Build Status](https://travis-ci.com/samsam2310/zbar.wasm.svg?branch=master)](https://travis-ci.com/samsam2310/zbar.wasm)
 
-A wasm build for C/C++ Zbar bar code scan library.
+A webassembly build for C/C++ Zbar bar code scan library.
+Webassembly can run on many morden browser without additional support, and is faster than many pure ECMAScript implementation.
+
+
+## Quick Start
+
+Online Demo: https://zbar.chino.taipei
+
+Install:
+``` bash
+npm install zbar.wasm
+```
+
+Quick example:
+
+``` javascript
+import Scanner from 'zbar.wasm';
+
+const loadImage = async src => {
+  // Load image
+  const imgBlob = await fetch(src).then(resp => resp.blob());
+  const img = await createImageBitmap(imgBlob);
+  // Make canvas same size as image
+  const canvas = document.createElement('canvas');
+  canvas.width = img.width;
+  canvas.height = img.height;
+  // Draw image onto canvas
+  const ctx = canvas.getContext('2d');
+  ctx.drawImage(img, 0, 0);
+  return {
+  	imageData: ctx.getImageData(0, 0, img.width, img.height),
+  	width: img.width,
+  	height: img.height
+  }
+}
+
+const main = async () => {
+  // Create a sannner object
+  const scanner = await Scanner({locateFile: file => ('data/' + file)});
+  const { imageData, width, height } = await loadImage('URL_TO_IMAGE');
+  const scanRes = scanner.scanQrcode(imageData.data, width, height);
+  if (scanRes.length > 0) {
+  	console.log('Find Qrcode: ' + scanRes);
+  }
+
+main();
+```
+
+
+## API
+
+`Scanner.scanQrcode(imgData, width, height)`
+
+#### Parameter
+
+* imgData
+
+	A `Uint8Array` Object or something compatible, representing a one-dimensional array containing the data in the RGBA order, with integer values between 0 and 255 (included). See [ImageData.data](https://developer.mozilla.org/en-US/docs/Web/API/ImageData/data).
+* width
+
+	The width of the image.
+* height
+
+	The height of the image.
+
+#### Return value
+
+A array contains decode Qrcode data strings. If nothing is found, a empty list is returned.
+
+
+## How to include
+
+Although Webassembly is cross-platform and can run with browser or nodejs, on the nodejs side you may want to use native C++ Zbar instead to get better performance.
+
+Therefore zbar.wasm is written with ES6 and recommended to load with babel + webpack.
+
+The .wasm 'glue' code generated by Emscripten requires some node builtins, but won't actually use them in a web environment. Add this to webpack.config.js to ignore them when building. (Have Tested with webpack v4)
+
+```
+{
+  ...
+  externals: {
+    'fs': true,
+    'path': true,
+  },
+  ...
+}
+```
+
+When initializing the scanner object, the script will try to load the `.wasm` binary file. This file `zbar.wasm` should be available through the internet (or accessable by nodejs on server side). The file can be served by CDN or use `copy-webpack-plugin`.
+
+Scanner takes a object as argument and mix it into Webassembly Module. One usefull usage is to pass a `locateFile` function to tell all the location of the file needed by Webassembly.
+
+For example:
+
+``` javascript
+const scanner = await Scanner({
+	locateFile: filename => ('https:/my.cdn.com/myproject/' + filename)
+});
+```
+
+For more details, see [Demo webpack.config.js](https://github.com/samsam2310/zbar.wasm/blob/gh-pages/webpack.config.js)