[FaB] Additional filters option - Keywords

#add “keyword” as filtering option, most notably “Legendary” and “Specilalization”

The current selection of filter is really rich and diverse but it’s missing at least 1 useful one, the ability to filter by keywords. While most are mainly useful when deckbuilding, more specific ones, like “Legendary” which limit the count of that card in a playset to 1 and thus be a crucial information for playset collector, or “Specialization” which limit to use of a card to a specific hero only.