Add vim modeline

Please don’t kill me.

Signed-off-by: Thomas Schneider <thosch97@gmail.com>
Use '~' instead of ' ' in name

Signed-off-by: Thomas Schneider <thosch97@gmail.com>
Gruppe/Einführung: Gruppendynamische Experimente

Signed-off-by: Thomas Schneider <thosch97@gmail.com>