Add migration examples to UPGRADE-6.0.md guide

Co-authored-by: Grotax <[email protected]>

Author: Copilot

docs/upgrades/UPGRADE-6.0.md

@@ -5,3 +5,42 @@ Several major changes in version 6.0:
  - The factory has been removed. Use `new` to construct your FeedIO instance: `new \FeedIo\FeedIo($client, $logger)`
  - Feed IO comes no longer bundled with a default HTTP client, but uses HTTPlug instead. To continue using Guzzle, please require `php-http/guzzle7-adapter`.
  - Feed IO does no longer set a custom user agent. However, HTTP clients usually add a default themselves. If the feed you want to read requires a specific user agent, please configure your HTTP client accordingly, before you inject it into Feed IO. 
+
+## Migrating from Factory
+
+### Before (5.x)
+```php
+use \FeedIo\Factory;
+
+$feedIo = Factory::create()->getFeedIo();
+```
+
+### After (6.0+)
+```php
+use \FeedIo\Adapter\Http\Client;
+use \Http\Discovery\Psr18ClientDiscovery;
+
+$client = new Client(Psr18ClientDiscovery::find());
+$feedIo = new \FeedIo\FeedIo($client);
+```
+
+### With Logging (6.0+)
+```php
+use \FeedIo\Adapter\Http\Client;
+use \Http\Discovery\Psr18ClientDiscovery;
+use Monolog\Logger;
+use Monolog\Handler\StreamHandler;
+
+$client = new Client(Psr18ClientDiscovery::find());
+$logger = new Logger('feed-io', [new StreamHandler('php://stdout')]);
+$feedIo = new \FeedIo\FeedIo($client, $logger);
+```
+
+### With Guzzle Client (6.0+)
+```php
+use \FeedIo\Adapter\Guzzle\Client;
+use \GuzzleHttp\Client as GuzzleClient;
+
+$client = new Client(new GuzzleClient());
+$feedIo = new \FeedIo\FeedIo($client);
+```