John Castrillon

I tried to see the live example and it came back as a 502 bad gateway.

update listings 11-01 and 11-03 with add function generated by cargo

1

This updates the testing code in chapter 11 to reflect what cargo will generate when running `cargo new adder --lib`.

### Check for existing issues - [x] Completed ### Misc notes This is a theme based on the [vscode-chester-atom](https://github.com/ceckenrode/vscode-chester-atom) theme. I already have a working PR for this here: https://github.com/zed-industries/extensions/pull/3330