feat(dealers): expand model by keywords

[Metawolve]

This pull request adds the keywords property to the dealers model.
The categories are now imported from the keys of the keywords.

Also, a few minor issues were fixed in the dealers import and dealer queries.

Example result with the new keywords:

"Categories": [
      "Commissions and Services",
      "Music and Audio",
      "Plushies"
    ],
    "Keywords": {
      "Commissions and Services": [
        "VR Integration",
        "Workshops, Classes, Tutorials"
      ],
      "Music and Audio": [
        "Music and Audio (Other)"
      ],
      "Plushies": [
        "Plushy Animals"
      ]
    },

[Fenrikur]

LGTM