document `push .. pop` pattern in `clox` about lox HOT 3 CLOSED

push_value(OBJECT_VAL(string__copy(name, (int)strlen(name), vm)), vm);
push_value(OBJECT_VAL(native_function__new(function, vm)), vm);
table__set(&vm->global_vars, AS_STRING(vm->value_stack[0]), vm->value_stack[1]);
pop_value(vm);
pop_value(vm);

memory__open_object_nursery(vm);
// e.g., `vm->nursery_start = vm->objects`

ObjectString* function_name = string__copy(name, (int)strlen(name), vm));
Value function = OBJECT_VAL(native_function__new(function, vm)));
// during a GC run (which might happen in `table__set`), we expose objects 
// between `vm->nursery_start` and `vm->objects` as roots so they are not 
// incorrectly disposed
table__set(&vm->global_vars, function_name, function);

memory__close_object_nursery(vm);
// e.g., `vm->nursery_start = NULL`