Provide additional default themes and/or theme examples

[cylewitruk]

Placeholder ticket 😄 There should be an example of overriding a theme, and it would be awesome to start a small contrib repo with different themes.

[fadeevab]

@cylewitruk There is! https://github.com/fadeevab/cliclack/blob/main/examples/theme.rs

[cylewitruk]

Awesome! Not sure how I missed that 😂 I do still think that providing a couple of "real" themes would be beneficial to adoption of cliclack.

I'm no designer, but I'd be happy to try to adopt some other CLI themes as time allows 🤘