this keyboard layout is based on a Apple US ANSI keyboard layout with the following changes
option + a
->ä
option + o
->ö
option + u
->ü
option + e
->€
option + shift + a
->Ä
option + shift + u
->Ü
option + shift + o
->Ö
option + shift + s
->ẞ
copy bundle into ~/Library/Keyboard\ Layouts/
or /Library/Keyboard\ Layouts/