Update Readme

README.md

@@ -1,20 +1,38 @@
+
 # Modern Spreadsheet
 
-- <span>High performance spreadsheet based on CanvasAPI.</span>
-- <span>TypeScript supported</span>
   
-<div>
-<span>Basic usage</span>
+
+-  High performance spreadsheet based on CanvasAPI.
+
+-  TypeScript supported
+
+  Basic usage
 
 ```js
 import { Spreadsheet } from  'modern_spreadsheet'
+
 import  'modern_spreadsheet/style.css'  // <= this is required
 
 const  target = document.getElementById('spreadsheet')
 
 const  sheet = new  Spreadsheet(target)
+//...
+
 ```
 
-<span>Load data</span>
+Save and load data
+```js
+function saveData() {
+	const serialized = sheet.serializeData()
+	localStorage.setItem('sheet_data', JSON.stringify(serialized))
+}
 
+function loadData() {
+	const data = localStorage.getItem('sheet_data')
+	const json = JSON.parse(data)
+	if(!json) return;
+	sheet.loadData(json)
+}
+```
 </div>