WebContent+Friends: Add get_element_tag_name IPC and plumbing

Author: https://github.com/TobyAsE
Commit: be6bbdaa3b
Pull-request: https://github.com/SerenityOS/serenity/pull/15730
Reviewed-by: https://github.com/linusg

Userland/Services/WebContent/WebContentServer.ipc

@@ -43,6 +43,7 @@ endpoint WebContentServer
     get_element_property(i32 element_id, String name) => (Optional<String> property)
     get_active_documents_type() => (String type)
     get_computed_value_for_element(i32 element_id, String property_name) => (String computed_value)
+    get_element_tag_name(i32 element_id) => (String tag_name)
 
     run_javascript(String js_source) =|