Issue with Pluralization in German Language for Umlauts

[peymansf2000]

I hope this message finds you well. I've identified an issue with the pluralization function in your GitHub repository when dealing with German words containing umlauts. The problem becomes apparent in cases where the plural form should include umlauts, but the function does not handle them correctly.

Here are specific examples:

word1 = 'Frucht'
pluralize(word1)
#should be 'Früchte'
Out[8]: 'Fruchte'

word2 = 'Apfel'
pluralize(word2)
#should be 'Äpfel'
Out[9]: 'Apfel'

word3 = 'Arzt'
pluralize(word3)
#should be 'Ärzte'
Out[10]: 'Arzte'

word4 = 'Anbaufläche'
pluralize(word4)
#it's true
Out[11]: 'Anbauflächen'

word5 = 'Fläche'
pluralize(word5)
# it's true
Out[12]: 'Flächen'

word6 = 'Stuhl'
pluralize(word6)
#should be 'Stühle'
Out[13]: 'Stuhle'

word7 = 'Flüssigkeit'
pluralize(word7)
#should be 'Flüssigkeiten'
#no 'en'!why!
Out[14]: 'Flüssigkeit'

word8 = 'Röhre'
pluralize(word8)
#it's true
Out[15]: 'Röhren'

word9 = 'Höhle'
pluralize(word9)
#it's true
Out[16]: 'Höhlen'

word10 = 'Ökonomie'
pluralize(word10)
#it's true
Out[17]: 'Ökonomien'

word11 = 'Loch'
pluralize(word11)
#should be 'Löcher'
Out[18]: 'Loche'