Adjust twitch integration configuration (home-assistant#11853)

* Add oauth token doc

* Adjust to latest config changes

* ✏️ Tweaks

* Remove optional config from example

Co-authored-by: Franck Nijhof <[email protected]>

source/_integrations/twitch.markdown

@@ -10,9 +10,22 @@ ha_iot_class: Cloud Polling
 
 The `twitch` platform will allow you to monitor [Twitch](https://www.twitch.tv/) channel status from within Home Assistant and setup automation based on the information.
 
-## Setup
+## Setup Client ID
 
-Create a new app at "Register Your Application" in the [Twitch developer portal](https://glass.twitch.tv/console/apps). Then get the **Client ID** for the new app.
+Create a new app at "Register Your Application" in the [Twitch developer portal](https://glass.twitch.tv/console/apps). Then get the __Client ID__ for the new application.
+
+## Setup OAuth Token
+
+To enable the follow and subscription attributes, the OAuth token is needed to get the right permissions on the Twitch API.
+If you don't need those, ignore the configuration setting: `token`.
+
+To get the OAuth token, visit the [OAuth Token Generator](https://twitchapps.com/tokengen/#), insert your __Client ID__ and `user_read user_subscriptions` inside __scopes__.
+
+Before clicking Summit (the broken image below the form), visit the [Twitch dev console](https://dev.twitch.tv/console) and add a new application.
+
+As __OAuth Redirect URLs__ add `https://twitchapps.com/tokengen/` and click __Create__
+.
+Back at the Token Generator, click the __Summit__ button, accept the consent screen and get your __OAuth Token__.
 
 ## Configuration
 
@@ -33,6 +46,10 @@ client_id:
   description: Your Twitch client ID.
   required: true
   type: string
+token:
+  description: Your Twitch OAuth Token.
+  required: false
+  type: string
 channels:
   description: List of channels names
   required: true