Examine source code of GemMarker

{
  "manifest_version": 3,
  "minimum_chrome_version": "88",
  "name": "GemMarker",
  "short_name": "GemMarker",
  "author": "perceptron8",
  "description": "Web Extension making 'The Settlers Online' collectibles easy to find!",
  "homepage_url": "https://gemmarker.com/",
  "version": "0.7.3",
  "browser_specific_settings": {
    "gecko": {
      "id": "{d6916fe4-cbac-4a26-9ba7-583f4b57c315}",
      "strict_min_version": "113.0"
    }
  },
  "icons": {
    "128": "icon.png"
  },
  "action": {
    "default_icon": {
      "128": "icon.png"
    },
    "default_title": "GemMarker",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.thesettlersonline.com/*",
        "https://www.tsotesting.com/*",
        "https://www.tsotesting2.com/*",
        "https://www.diesiedleronline.de/*",
        "https://www.juego-thesettlersonline.com/*",
        "https://www.thesettlersonline.com.br/*",
        "https://www.thesettlersonline.cz/*",
        "https://www.thesettlersonline.es/*",
        "https://www.thesettlersonline.fr/*",
        "https://www.thesettlersonline.gr/*",
        "https://www.thesettlersonline.it/*",
        "https://www.thesettlersonline.net/*",
        "https://www.thesettlersonline.nl/*",
        "https://www.thesettlersonline.pl/*",
        "https://www.thesettlersonline.ro/*",
        "https://www.thesettlersonline.ru/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "declarativeNetRequest",
    "storage",
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "web_accessible_resources": [
    {
      "resources": [
        "sprites/ExhaustedField.png",
        "sprites/ExhaustedMine.png",
        "sprites/ExhaustedMarble.png",
        "sprites/aa4bacf36c96657605ef8245ddefadbfce44b719_N.png",
        "sprites/467e09c4a79e72fec32dd8e61f50a97cd982a148_N.png",
        "sprites/88eeec27dc611d4bb485875cc319264b5ee27220_N.png",
        "sprites/01cd4ebcc722aa26b63abd54703737e69d3727be_N.png",
        "sprites/ad04453b0ab115dcaf1148636d870e01645a1bfe_N.png",
        "sprites/4e5010cb4aa113d1eb3b695f31ac2cba44aed21b_N.png",
        "sprites/258570a9c250407e2cf5cfa4d6a7bcba86e7376e_N.png"
      ],
      "matches": [
        "https://www.thesettlersonline.com/*",
        "https://www.tsotesting.com/*",
        "https://www.tsotesting2.com/*",
        "https://www.diesiedleronline.de/*",
        "https://www.juego-thesettlersonline.com/*",
        "https://www.thesettlersonline.com.br/*",
        "https://www.thesettlersonline.cz/*",
        "https://www.thesettlersonline.es/*",
        "https://www.thesettlersonline.fr/*",
        "https://www.thesettlersonline.gr/*",
        "https://www.thesettlersonline.it/*",
        "https://www.thesettlersonline.net/*",
        "https://www.thesettlersonline.nl/*",
        "https://www.thesettlersonline.pl/*",
        "https://www.thesettlersonline.ro/*",
        "https://www.thesettlersonline.ru/*"
      ]
    }
  ],
  "host_permissions": [
    "https://www.tsotesting.com/",
    "https://www.tsotesting2.com/",
    "https://ubistatic-a.akamaihd.net/",
    "https://www.diesiedleronline.de/",
    "https://www.juego-thesettlersonline.com/",
    "https://www.thesettlersonline.com/",
    "https://www.thesettlersonline.com.br/",
    "https://www.thesettlersonline.cz/",
    "https://www.thesettlersonline.es/",
    "https://www.thesettlersonline.fr/",
    "https://www.thesettlersonline.gr/",
    "https://www.thesettlersonline.it/",
    "https://www.thesettlersonline.net/",
    "https://www.thesettlersonline.nl/",
    "https://www.thesettlersonline.pl/",
    "https://www.thesettlersonline.ro/",
    "https://www.thesettlersonline.ru/"
  ]
}