patch 9.0.1001: classes are not documented or implemented yet

Problem:    Classes are not documented or implemented yet.
Solution:   Make the first steps at documenting Vim9 objects, classes and
            interfaces.  Make initial choices for the syntax.  Add a skeleton
            implementation.  Add "public" and "this" in the command table.
diff --git a/src/errors.h b/src/errors.h
index 2fc80c5..cf30221 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -3345,3 +3345,7 @@
 	INIT(= N_("E1312: Not allowed to change the window layout in this autocmd"));
 EXTERN char e_not_allowed_to_add_or_remove_entries_str[]
 	INIT(= N_("E1313: Not allowed to add or remove entries (%s)"));
+#ifdef FEAT_EVAL
+EXTERN char e_class_name_must_start_with_uppercase_letter_str[]
+	INIT(= N_("E1314: Class name must start with an uppercase letter: %s"));
+#endif