Request: add common german symbols ß, ä, ë, ö, ü to Old English

[nach0]

Describe the solution you'd like
It would be nice to add the character Eszet (ß) and the symbols for vowels with diacritic accent (umlaut).

Describe alternatives you've considered
Currently the app displays these symbols (ß, ä, ë, ö, ü) with the regular system font when typing in the Old English or Old English Bold fonts.

Additional context
German is probably the only language that still uses to some extent the Blackletter kind of script that Old English represents in Irregular Expressions, however some common German symbols (ß, ä, ë, ö, ü) are missing and they would be especially useful in this font.