add function execution to the VM

src/main.rs

@@ -133,7 +133,7 @@ fn main() {
             vm.run();
             println!("\n");
             println!("Registers: {:?}", vm.registers);
-            println!("Program Counter: {}", vm.pc);
+            println!("Stack: {:?}", vm.stack);
             println!("Memory: {:?}", vm.memory);
             /*let mut executor = Executor::new(ast, 100);
             executor.resume();