Add similarity information to entries

[LorenzoMinto]

To each entry in the feed, we add an index field and similar_entries field that reports the indexes of other entries whose titles are similar above a certain threshold (set in config.py).

{
    "category": "Top News",
    "publish_time": "2022-09-21 15:42:34",
    "url": "https://edition.cnn.com/2022/09/21/politics/joe-biden-united-nations-general-assembly/index.html",
    "img": "https://cdn.cnn.com/cnnnext/dam/assets/220915115300-04-biden-rose-garden-0915-super-169.jpg",
    "title": "Russia's war to extinguish Ukraine 'should make your blood run cold,' Biden says",
    "description": "President Joe Biden returns to the green-marbled United Nations stage Wednesday hours after Russia's president announced in a provocative speech an escalation in his war effort in Ukraine, setting up a rhetorical showdown between the two leaders on the international stage.",
    "content_type": "article",
    "publisher_id": "caae10247386499c8496985ac0ad863ebabe95f760370cdb72c8e7d68d0355ad",
    "publisher_name": "CNN",
    "creative_instance_id": "",
    "url_hash": "708b46d85691bbe71cc65f294cf9e8a7a60512eb5f4358d3233c15d69ab5b8cc",
    "index": "4",
    "padded_img": "https://cdn.cnn.com/cnnnext/dam/assets/220915115300-04-biden-rose-garden-0915-super-169.jpg",
    "score": 30.037019041241365,
    "similar_entries": [
      "8",
      "13",
      "23",
      "31",
      "36",
      "43",
      "45"
    ]
  }

This information can be used by the client to improve the quality of the feed by either: (1) increasing feed diversity by spacing out entries that have similar titles, (2) grouping together similar entries.