test: add time is builtin test

src/builtins/mod.rs

@@ -134,6 +134,11 @@ mod tests {
         assert!(is_builtin("quote"));
     }
 
+    #[test]
+    fn test_is_builtin_time() {
+        assert!(is_builtin("time"));
+    }
+
     #[test]
     fn test_is_builtin_notabuiltin() {
         assert!(!is_builtin("notabuiltin"))