LibWebView+WebConent: Add an IPC to get an element's enabled state

Author: https://github.com/trflynn89
Commit: 683c99f299
Pull-request: https://github.com/SerenityOS/serenity/pull/15909
Reviewed-by: https://github.com/linusg ✅

Userland/Services/WebContent/WebContentServer.ipc

@@ -49,6 +49,7 @@ endpoint WebContentServer
     get_element_text(i32 element_id) => (String text)
     get_element_tag_name(i32 element_id) => (String tag_name)
     get_element_rect(i32 element_id) => (Gfx::IntRect rect)
+    is_element_enabled(i32 element_id) => (bool enabled)
 
     webdriver_execute_script(String body, Vector<String> json_arguments, Optional<u64> timeout, bool async) => (Web::WebDriver::ExecuteScriptResultType result_type, String json_result)