Examine source code of RarityRank

{
  "manifest_version": 2,
  "name": "RarityRanks",
  "version": "1.0.4",
  "icons": {
    "16": "assets/icons/favicon-16.png",
    "32": "assets/icons/favicon-32.png",
    "48": "assets/icons/favicon-48.png",
    "128": "assets/icons/favicon-128.png"
  },
  "description": "",
  "homepage_url": "https://rarityranks.io/",
  "short_name": "RarityRanks",
  "permissions": [
    "tabs",
    "storage",
    "http://opensea.io/*",
    "https://opensea.io/*",
    "http://market.x.immutable.com/*",
    "https://market.x.immutable.com/*"
  ],
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "author": "dmitry_pogorelov",
  "applications": {
    "gecko": {
      "id": "ticket.tracker123@gmail.com"
    }
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "assets/icons/favicon-16.png",
      "32": "assets/icons/favicon-32.png",
      "48": "assets/icons/favicon-48.png",
      "128": "assets/icons/favicon-128.png"
    },
    "default_title": "RarityRanks",
    "browser_style": false
  },
  "background": {
    "scripts": [
      "js/background.bundle.js"
    ]
  },
  "web_accessible_resources": [
    "page-popup.html",
    "updated.html",
    "assets/icons/logo-lines.svg",
    "assets/icons/logo-inside.svg",
    "assets/fonts/OpenSans400.woff2",
    "assets/fonts/OpenSans600.woff2"
  ],
  "content_scripts": [
    {
      "matches": [
        "http://opensea.io/*",
        "https://opensea.io/*",
        "http://market.x.immutable.com/*",
        "https://market.x.immutable.com/*"
      ],
      "js": [
        "js/contentScript.bundle.js"
      ]
    }
  ]
}