feat(ast): data as void* and basic helpers

src/utils/ast/ast.c

@@ -0,0 +1,23 @@
+#include "ast.h"
+
+#include <stdbool.h>
+
+bool ast_is_if(struct ast *node)
+{
+    return node->type == AST_IF;
+}
+
+bool ast_is_cmd(struct ast *node)
+{
+    return node->type == AST_CMD;
+}
+
+struct ast_if *ast_get_if(struct ast *node)
+{
+    return (struct ast_if *)node->data;
+}
+
+struct ast_cmd *ast_get_cmd(struct ast *node)
+{
+    return (struct ast_cmd *)node->data;
+}