🐛 fix bug in json.cpp & add std/argparse.nas

test/argparse_test.nas

@@ -0,0 +1,11 @@
+# use module.libjson;
+
+# libjson.stringify(math.tan);
+
+# println(libjson.get_error());
+use std.argparse;
+
+var args = argparse.new("test cli");
+args.add_command("--what", "-w", "what-what");
+args.add_subparser("what", "what-what");
+args.parse();