feat: adding German plurals to the oils in Ingredients.pm (#9304)

* adding German

* Update Ingredients.pm

* refactor to improve support for German

* fix typos

* fixes

* Update lib/ProductOpener/Ingredients.pm

Co-authored-by: benbenben2 <[email protected]>

* fixes and tests

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Co-authored-by: Stéphane Gigandet <[email protected]>
Co-authored-by: benbenben2 <[email protected]>