lang: ast: define ast_node_type for some fundamental expression components

lang/ast/string.c

@@ -0,0 +1,7 @@
+#include "ctx.h"
+#include "node.h"
+
+struct ast_node_type string_node_ops = {
+        .n_state_size = sizeof(struct parser_state),
+        .n_node_size = sizeof(struct ivy_ast_string_node),
+};