Add WorldClockView

[ryonakano]

As requested in https://github.com/orgs/elementary/discussions/171

[hrstwn]

Thank you!
Are you open to some design suggestions?

[ryonakano]

@hrstwn Yes, I would appreciate it if you, who has requested this feature, would give me suggestions or inputs about desigins, features, etc. 🎉

[hrstwn]

Thank you 🙌
Some needed basic info:

• Hours difference to our local timezone (1 hour ahead/behind, etc.)
• See if the city's date is still yesterday or tomorrow, compared to our timezone
• Some indicator to show if it's night or daytime there (an icon and color indicator would be nice)
• country code, maybe (?) Sometimes I forget in what country the city located

[hrstwn]

by the way, I made a mockup

[ryonakano]

Wow, thank you for your nice mockup and suggestions! It is helpful.
Specifically I really like the idea of night/daytime indicator! There are two icons weather-clear-night and weather-clear available in elementary OS so it shouldn't difficult to implement this desigin.

[ryonakano]

Implemented these things:

• Hours difference to our local timezone (1 hour ahead/behind, etc.)
• See if the city's date is still yesterday or tomorrow, compared to our timezone
• Some indicator to show if it's night or daytime there (an icon and color indicator would be nice)

and now it looks like this:

TODO:

• The location of city (it's hardcoded in the above screenshot. It would be nice if there are library to get it)
• Provide a way to add new world clock
• Provide a way to remove new world clock
• Automatically update the time, delta, and indicator per minute