suggestion: allow "wildcard" POS for stopwords

[arc12]

The current approach which specifies stopwords as
lemma: [POS]
presents two issues:

1. There are some terms which POS taggers will fail over. For example, Spacy labels "AI" (artificial intelligence) as PROPN
2. If I create software to be used by people without linguistic knowledge, I cannot expect them to know about POS.

As a work-around, it is necessary to specify all POS tags, which is rather inelegant.