patch 8.2.1685: Vim9: cannot declare a constant value

Problem:    Vim9: cannot declare a constant value.
Solution:   Introduce ":const!".
diff --git a/src/errors.h b/src/errors.h
index c76afbc..badbabd 100644
--- a/src/errors.h
+++ b/src/errors.h
@@ -258,4 +258,12 @@
 	INIT(= N_("E1116: assert_fails() fifth argument must be a string"));
 EXTERN char e_cannot_use_bang_with_nested_def[]
 	INIT(= N_("E1117: Cannot use ! with nested :def"));
+EXTERN char e_cannot_change_list[]
+	INIT(= N_("E1118: Cannot change list"));
+EXTERN char e_cannot_change_list_item[]
+	INIT(= N_("E1119: Cannot change list item"));
+EXTERN char e_cannot_change_dict[]
+	INIT(= N_("E1120: Cannot change dict"));
+EXTERN char e_cannot_change_dict_item[]
+	INIT(= N_("E1121: Cannot change dict item"));
 #endif