LanguageServers: Add function to collect TODO entries in a document

Author: https://github.com/guerinoni
Commit: 26a7356e90
Pull-request: https://github.com/SerenityOS/serenity/pull/6614
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/itamar8910 ✅
Reviewed-by: https://github.com/linusg

Userland/DevTools/HackStudio/LanguageServers/LanguageClient.ipc

@@ -3,4 +3,5 @@ endpoint LanguageClient
     auto_complete_suggestions(Vector<GUI::AutocompleteProvider::Entry> suggestions) =|
     declaration_location(GUI::AutocompleteProvider::ProjectLocation location) =|
     declarations_in_document(String filename, Vector<GUI::AutocompleteProvider::Declaration> declarations) =|
+    todo_entries_in_document(String filename, Vector<String> todo_entries) =|
 }