Add back the dataset pretty-printer for ad-hoc analyses of the datasets stored on disk.

Example usage:

$ cargo xtask pretty-print-dataset data/datasets/naturdetektive-bfn/-lexikon-zum-lesen-biologische-vielfalt-f
arben-in-der-natur.html 
{
  "title": "Farben in der Natur",
  "description": "Ein Lernangebot für Kinder. Jetzt wird's bunt Die Natur ist bunt. Blumen, Schmetterlinge, Käfer leuchten in allen Farben um die Wette. Aber warum tun die das eigentlich? Und wie entstehen die unterschiedlichen Farben?",
  "origins": [
    "/Bund/BfN/Naturdetektive"
  ],
  "license": {
    "path": "/closed/all-rights-reserved",
    "label": "all-rights-reserved",
    "url": "https://en.wikipedia.org/wiki/All_rights_reserved"
  },
  "mandatory_registration": false,
  "tags": [
    {
      "Umthes": {
        "id": 80008,
        "label": "Käfer"
      }
    },
    {
      "Umthes": {
        "id": 137313,
        "label": "Schmetterling"
      }
    },
    {
      "Umthes": {
        "id": 6715160,
        "label": "Leuchte"
      }
    },
    {
      "Umthes": {
        "id": 82583,
        "label": "Kind"
      }
    }
  ],
  "source_url": "https://naturdetektive.bfn.de/lexikon/zum-lesen/biologische-vielfalt/farben-in-der-natur.html",
  "machine_readable_source": false,
  "language": {
    "id": "German",
    "path": "/Deutsch",
    "label": "Deutsch"
  },
  "quality": {
    "findability": {
      "title": 0.0,
      "description": 0.0,
      "spatial": "NoRegion",
      "spatial_score": 0.0,
      "temporal": false,
      "keywords": 0.0,
      "identifier": false,
      "score": 0.0
    },
    "accessibility": {
      "landing_page": "Unknown",
      "landing_page_score": 0.0,
      "direct_access": false,
      "publicly_accessible": false,
      "score": 0.0
    },
    "interoperability": {
      "open_file_format": false,
      "media_type": false,
      "machine_readable_data": false,
      "machine_readable_metadata": false,
      "score": 0.0
    },
    "reusability": {
      "license": "NoInformation",
      "license_score": 0.0,
      "contact_info": false,
      "publisher_info": false,
      "score": 0.0
    },
    "score": 0.0
  }
}