LibWeb+UI: Add internals API to set browser zoom

Author: https://github.com/InvalidUsernameException
Commit: 5cc9a5802d
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2982
Reviewed-by: https://github.com/AtkinsSJ

Services/WebContent/WebContentClient.ipc

@@ -97,6 +97,8 @@ endpoint WebContentClient
     did_finish_text_test(u64 page_id, String text) =|
     did_set_test_timeout(u64 page_id, double milliseconds) =|
 
+    did_set_browser_zoom(u64 page_id, double factor) =|
+
     did_find_in_page(u64 page_id, size_t current_match_index, Optional<size_t> total_match_count) =|
 
     request_worker_agent(u64 page_id) => (IPC::File socket) // FIXME: Add required attributes to select a SharedWorker Agent