Compile learning-friendly word frequency lists for all of the included languages

[jqhoogland]

Word frequency lists are a useful reference for deciding what vocab to prioritize.

The problem is that most lists you'll find online are not cleaned (so "run", "runs", "ran") show up as separate entries, and the entries lack extra information (like gender, part of speech, etc.) that make it easier to turn them into flash cards.

So the idea is to come up with "standard" learning-friendly word-frequency-ordered lists of vocab.