Update PeerTube API for videos to filter on `categoryOneOf=null` for Uncategorized

[mblomdahl]

When listing videos, we can pass the query param ?categoryOneOf=2 to filter out videos in category 2 "Films". See API docs here: https://docs.joinpeertube.org/api-rest-reference.html#tag/Video/operation/getVideos

Example:

curl -s 'https://peertube2.cpy.re/api/v1/videos?isLocal=true&categoryOneOf=2' | jq '.data[].category'
{
  "id": 2,
  "label": "Films"
}
{
  "id": 2,
  "label": "Films"
}

For implementing OwnTube-tv/web-client#153, it is necessary to apply this filter, or we'll be stuck in having to list all videos and then filter out the ones with category.id=null on the client side (which is not an option). Can we please update the root-level GET /api/v1/videos and GET /api/v1/video-channels/{channelHandle}/videos API endpoints to support filtering on uncategorized?