Optionally show sugar and flour as dl

[falk-hueffner]

https://www.allrecipes.com/recipe/10813/best-chocolate-chip-cookies/

Also here, the 1 cup of white sugar is converted to 200g, whereas I'd prefer if it was dl, because that's how we measure things in Finland and I assume other Nordic countries. 1 cup of butter indeed IS better as grams, so no need to change that. But also flour is converted to grams, which would be better as dl. Chocolate chips and walnuts are in dl, which is good!

Perhaps, if people wish to have sugar and flour as grams instead, there could be a simple preferences page for these really common ingredients, in case there's no default usage for them.

Originally posted by @Ianuarius in https://github.com/falk-hueffner/metric-cooking/issues/13#issuecomment-778608619