Allow users to customize the start day of the week

[steindvart]

Problem

Currently, in Habitica, the week always starts on Saturday for all users. This does not suit everyone and can feel unnatural or confusing.

Proposal

Add a setting that allows users to choose the starting day of the week (for example: Saturday, Sunday, or Monday) according to their preference.

Arguments

• Different regions and cultures have different traditions for which day starts the week. For example, in the US the week usually starts on Sunday, while in many European countries it starts on Monday.
• Forcing all users to have Saturday as the start of the week reduces usability and user experience.
• Allowing users to set their preferred start day will make Habitica more comfortable and familiar for everyone, no matter where they are from.

[somelamedude-git]

Hey maintainers! I would like to work on this issue, please assign this to me