Add support for custom user agent in screenshot generation

This update includes a new service, `ScreenshotSubscriber`, that disables profiler if the user agent matches a specified one. Also, a custom user agent can now be used when using the `CreateScreenshotCommand`, and this setting is configurable in `web_client.php`. Finally, some PHPStan warnings were addressed and the "ext-sockets" package was added to the dev dependencies.

src/Command/CreateScreenshotCommand.php

@@ -20,6 +20,7 @@
 use Symfony\Component\Panther\Client;
 use Symfony\Component\Yaml\Yaml;
 use Throwable;
+use function assert;
 use function count;
 
 #[AsCommand(