Option to have calendar start week Sunday

[sasukeiscool]

Use case

The calendar on wger can only be set to start on Monday, but many countries use Sunday as the start of the week.

Proposal

Add option in settings to choose day to start week with.

[Dieterbe]

perhaps getting the users locale will provide this info to us.
e.g. https://stackoverflow.com/questions/50923906/how-to-get-timezone-language-and-county-id-in-flutter-by-the-location-of-device