Implement the --lines option

[fabianscode]

tested with various options and scale

[fabianscode]

Thanks for reviewing! I agree with you on the arrow keys. But since the original dmenu also does not implement dynamic height depending on the amount of non-empty lines, I suppose it would be better to simply make this functionality available through a patch.

[fabianscode]

@nyyManni could you take a look at it, please? :)

[fabianscode]

@sid115 arrow keys should be implemented now