Support other suffixes besides "U" for absence days.

[Scriptim]

When attempting to enter an absence due to illness in my time sheet, I was surprised to find that this is apparently not possible with this tool.

I would like to ask you to reconsider supporting the suffixes "K" (sick days), "F" (holidays) and "S" (other), especially the former, in addition to "U" (vacation) in order to be able to specify further absence reasons.

The implementation could be done analogous to vacation days with boolean flags (e. g. sickness), in which case the corresponding suffix should be written into the TeX file accordingly. Besides, I think it makes sense to support this, since these suffixes are also listed in the generated PDFs:

Summe in vollen Stunden und Minuten ohne Pause (Std:Min); bei Abwesenheit können auch folgende Kürzel eingetragen werden: U=Urlaub, K=Krankheit, F=Feiertag, S=Sonstiges