feat: lambda functions

lisp.h

@@ -26,6 +26,7 @@ typedef enum e_NodeKind {
     NODE_KIND_LIST,
     NODE_KIND_NUMBER,
     NODE_KIND_FUNCTION,
+    NODE_KIND_LAMBDA,
 } NodeKind;
 
 typedef struct s_Node Node;
@@ -46,6 +47,10 @@ struct s_Node {
             Nob_String_View name;
             LispFunction apply;
         } as_function;
+        struct {
+            Nodes *params;
+            Node *body;
+        } as_lambda;
     };
 };