[Feat]: Create a UI-Design for "User Settings"

**😒 Is your feature request related to a problem? Please describe.**
As a user i want to have a page, where i can change my basic settings. Currently i only have the chance to change the theme from light to dark.

**🤔 Describe the solution you'd like**
The current implementation of settings is pretty basic. You have the option to change the theme by clicking on a setting-icon in the top right of the application. This opens a small overlay. But the user should make more settings, if the application grows like:

* change the username
* change the email
* change the password
* delete the account
* export saved user data
* contact the support
* change the language (can also be at the settings-overlay)

The UI should be easily exandable for more settings.