Ingestion code should refer to venue type for WS (workshop) designation

#9158 and #9642 instituted `"type": "workshop"` in venues.json, which is used by the homepage. Going forward, we need to maintain this for new volumes.

@mjpost in https://github.com/acl-org/acl-anthology/issues/9158#issuecomment-5203448187:

>> I have noticed previously that WS annotations are all over the map. I think the long-term solution is to add a field in venues.json that distinguishes this. For now, checking the latest volume title for "Workshop" or "Shared Task" should be good enough—I don't think TextGraphs would qualify as major even by conference standards. [it has 230 papers / 599 authors]
>
> This is true. At ingestion time, I have to add the `-w` flag which automatically adds `ws`. However, sometimes colocated events are not workshops (e.g., IWSLT, WMT, CoNLL).

See also #1117