update doc

Author: zhengqingxin

README.md

@@ -1,8 +1,50 @@
 # think-session-mysql
 Use Mysql to store session for ThinkJS
 
-## Create Database
 
+## Install
+
+```
+npm install think-session-mysql
+```
+
+## How to use
+
+config file `src/config/adapter.js`, add options:
+
+```js
+const mysqlSession = require('think-session-mysql');
+exports.session = {
+  type: 'mysql',
+  common: {
+    cookie: {
+      name: 'thinkjs',
+      //maxAge: '',
+      //expires: '',
+      path: '/',  //a string indicating the path of the cookie
+      //domain: '',
+      //secure: false,
+      //keys: [],
+      httpOnly: true,
+      sameSite: false,
+      signed: false,
+      overwrite: false
+    }
+  },
+   mysql:{
+    handle:mysqlSession,
+    database:'think_test',
+    prefix:'think_',
+    host:'127.0.0.1',
+    port:'3306',
+    user:'root',
+    password:''
+  }
+}
+```
+
+## Create Database
+`think_` is the prefix in `adapter.js`
 ```
   DROP TABLE IF EXISTS `think_session`;
   CREATE TABLE `think_session` (
@@ -15,5 +57,3 @@ Use Mysql to store session for ThinkJS
     KEY `expire` (`expire`)
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
 ```
-
-`think_` is the prefix in `db.config`