docs: add user sessions plugin preview image and update documentation

AdminForth/1900/image

Author: yaroslav8765

adminforth/documentation/docs/tutorial/09-Plugins/31-user-sessions.md

@@ -13,6 +13,8 @@ This plugin stores every issued session in a key-value adapter, shows them to th
 settings page, and lets them revoke any session. Logout revokes the session too, so its token stops
 working right away.
 
+![Active sessions page](/img/previews/user_sessions.png)
+
 ## Installation
 
 ```bash

adminforth/documentation/src/pages/index.tsx

@@ -83,6 +83,12 @@ const images = [
     link: '/docs/tutorial/Plugins/two-factors-auth/',
     description: 'RFC 6238-Compliant TOTP-Based & WebAuthn PassKeys 2FA will add additional security layer (login and preferred actions)'
   },
+  {
+    original: require('@site/static/img/previews/user_sessions.png').default,
+    title: 'User Sessions Plugin - revoke access from any device',
+    link: '/docs/tutorial/Plugins/user-sessions/',
+    description: 'Every browser signed into the panel, with IP, country and last use, revocable in one click and really signed out on logout'
+  },
   {
     original: require('@site/static/img/previews/branding.png').default,
     title: 'Branding and theming',