feature: add `format_alt` and `format_list` to all blocks about i3status-rust

[bim9262]

I'm sure some of the other non-interactive would benefit from having an alt format option. Instead of a format list option though mayt it would be better to allow a single or list of alt formats so that we don't need to set both.

See the Untagged section: https://serde.rs/enum-representations.html

The clock block may be interesting to you check out to see how we added the ability to display different timezones. While it's not actually a different format it's similar in concept.

[bim9262]

I don't think that we'd want to make every block have an alt format or list of formats. For example take a look at the pomodoro block which has several states in which clicking/scrolling have different actions.

[martinpelikan]

@bim9262 Thank you for the quick response.

Shall I change the request to only modify external_ip then? I suggested the change as a default because most blocks appear to follow the same pattern, while the interactive ones are more of an exception. Looking closer, there probably isn't much benefit, and might actually complicate existing code rather than simplify it.