examples: run clippy and fix issues

[jaudiger]

Hello there, it's quite a while the last time I opened a PR here. This time I just ran clippy in the examples folder, and resolved the issues that were reported.

Please let me know if you don't want this PR as is.

[fdncred]

Let's think about it because this crate is a pain to update for nushell because we publish a new version, then we have to wait for lscolors to publish a new version, then we have to wait for reedline, and then finally we can use it in nushell. So, if it's not significant changes, I'm inclined to just wait on this until the next significant change.

[jaudiger]

Sure, I understand. I did open one last PR (#59) but on the source folder this time. It has the advantages to derive few must_use macro. But I'm opened to updating both PR if needed, of course.

[kubouch]

When I run cargo clippy in the examples/ folder, nothing shows up.