add init description

Author: Michael Kechinov

Diff for: .ruby-version

@@ -0,0 +1 @@
+2.7.0

Diff for: source/index.html.md

@@ -4,6 +4,7 @@ title: REES46 API Reference
 language_tabs:
   - shell
   - javascript
+  - swift
 
 toc_footers:
   - <a href='#'>Sign Up for a Developer Key</a>
@@ -39,6 +40,45 @@ curl "https://api.rees46.com/?shop_id=357382bf66ac0ce2f1722677c59511"
 You must replace <code>357382bf66ac0ce2f1722677c59511</code> with your shop's API key.
 </aside>
 
+# Initialize
+
+## Start session
+
+`GET https://api.rees46.com/init_script`
+
+```shell
+curl https://api.rees46.com/init_script?ssid=SSID&shop_id=SHOPID&v=3&seance=SEANCE_ID&referrer=REF_URL
+```
+
+```javascript
+(function(r){window.r46=window.r46||function(){(r46.q=r46.q||[]).push(arguments)};var s=document.getElementsByTagName(r)[0],rs=document.createElement(r);rs.async=1;rs.src='//cdn.rees46.com/v3.js';s.parentNode.insertBefore(rs,s);})('script');
+r46('init', 'SHOPID');
+```
+
+```swift
+import REES46
+var sdk = createPersonalizationSDK(shopId: "SHOPID")
+```
+
+Before using SDK or API you have to initialize SDK. Initialization takes current user identifier and requests API for project settings and this user preferences. 
+
+If you don't have user's identifier (new user), you have to request API's `init` method to generate new one. Store this identifier (it's named `ssid`) in local storage of mobile application or in database: you'll need it for the future requests to API. 
+
+<aside class="notice">
+This method must be requested on every opened page on the website. And only once, when you launch mobile app.
+</aside>
+
+
+### Query Parameters
+
+Parameter | Required | Description
+--------- | ------- | -----------
+shop_id | true | Your API key
+ssid | false | Is mandatory if you have it. Request without `ssid` will generate new one in our DB. Use it as user ID for future requests.
+v | true | Version. Just use `3` as value.
+seance | true | User's temporary identifier for the current session. Must be regenerated every time user starts new session. Just unique string: `uuid8` is ok.
+referrer | false | Referrer page URL for web integration.
+
 # Mobile push tokens
 
 ## Create new token