WebContent: Add IPC call to get window handle from WebContent client

Author: https://github.com/kalenikaliaksandr
Commit: 48e0789a17
Pull-request: https://github.com/SerenityOS/serenity/pull/17855
Reviewed-by: https://github.com/linusg
Reviewed-by: https://github.com/trflynn89 ✅

Userland/Services/WebContent/WebContentServer.ipc

@@ -9,6 +9,8 @@
 
 endpoint WebContentServer
 {
+    get_window_handle() => (String handle)
+
     connect_to_webdriver(DeprecatedString webdriver_ipc_path) =|
 
     update_system_theme(Core::AnonymousBuffer theme_buffer) =|