Examine source code of Who Deleted Me - Unfriend Finder

{
  "author": "Who Deleted Me",
  "background": {
    "scripts": [
      "vendor/webextension-polyfill/dist/browser-polyfill.js",
      "vendor/dexie/dist/dexie.js",
      "background.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "16": "icons/icon16.png",
      "19": "icons/icon19.png",
      "32": "icons/icon32.png",
      "38": "icons/icon38.png",
      "48": "icons/icon48.png",
      "64": "icons/icon64.png",
      "96": "icons/icon96.png",
      "100": "icons/icon100.png",
      "128": "icons/icon128.png"
    },
    "default_title": "Who Deleted Me"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.deleted.io/*"
      ],
      "js": [
        "vendor/webextension-polyfill/dist/browser-polyfill.js",
        "wdm-content.js"
      ]
    }
  ],
  "description": "Keep track of who unfriends you on social networks.",
  "developer": {
    "name": "Who Deleted Me",
    "url": "https://www.deleted.io"
  },
  "homepage_url": "https://www.deleted.io",
  "name": "Who Deleted Me - See Who Unfriends You",
  "icons": {
    "16": "icons/icon16.png",
    "19": "icons/icon19.png",
    "32": "icons/icon32.png",
    "38": "icons/icon38.png",
    "48": "icons/icon48.png",
    "64": "icons/icon64.png",
    "96": "icons/icon96.png",
    "100": "icons/icon100.png",
    "128": "icons/icon128.png"
  },
  "manifest_version": 2,
  "permissions": [
    "*://*.deleted.io/",
    "*://*.facebook.com/"
  ],
  "short_name": "Who Deleted Me",
  "version": "3.0.10",
  "browser_specific_settings": {
    "gecko": {
      "id": "whodeletedme@deleted.io"
    }
  }
}