Update README

Author: nioc

README.md

@@ -2,6 +2,8 @@
 
 [![license: AGPLv3](https://img.shields.io/badge/license-AGPLv3-blue.svg)](https://www.gnu.org/licenses/agpl-3.0)
 [![GitHub release](https://img.shields.io/github/release/nioc/netatmo-nodejs-api.svg)](https://github.com/nioc/netatmo-nodejs-api/releases/latest)
+[![npm](https://img.shields.io/npm/dt/netatmo-nodejs-api)](https://www.npmjs.com/package/netatmo-nodejs-api)
+[![npms.io (final)](https://img.shields.io/npms-io/final-score/netatmo-nodejs-api)](https://www.npmjs.com/package/netatmo-nodejs-api)
 
 Node.js API wrapper for Netatmo API.
 
@@ -57,6 +59,37 @@ try {
 }
 ```
 
+### Authenticate wrapper (try access token, refresh token or client credentials)
+
+You can use the `authenticate` method which wrap 3 authentication methods.
+
+```js
+const { NetatmoClient, SCOPE_BASIC_CAMERA } = require('netatmo-nodejs-api')
+
+// you need to set your own information
+const clientId = '60...'
+const clientSecret = 'abc...'
+const username = 'user@domain'
+const password = 'pass'
+let refreshToken = ''
+let accessToken = ''
+let expiresInTimestamp = 0
+
+try {
+  // create client
+  const client = new NetatmoClient(clientId, clientSecret, SCOPE_BASIC_CAMERA, { timeout: 1000 })
+
+  // authenticate
+  ({ accessToken, refreshToken, expiresInTimestamp } = await client.authenticate(accessToken, refreshToken, expiresInTimestamp, username, password))
+  // you should store accessToken, refreshToken, expiresInTimestamp for further request
+
+  // get data
+  const homes = await client.getHomes()
+} catch (error) {
+  console.log(error)
+}
+```
+
 ## Versioning
 
 netatmo-nodejs-api is maintained under the [semantic versioning](https://semver.org/) guidelines.