Code Formatting Setup

[SoulKa]

In order to prevent code changes for actually untouched code, we want to have a single formatting rule which always applies. This also enforces correctly formatted code on commits.

Currently, we often have differently formatted code for different users.

Acceptance Criteria

• There's a prettier configuration (or similar) that defines a single source of truth for our code formatting. This actually already exists
• Incorrect formatted code cannot be committed or raises an error in our CI pipeline
• If applicable: documentation exists how to setup automatic formatting in IntelliJ and VSCode