Examine source code of MangasSubscriber

{
  "manifest_version": 2,
  "name": "MangasSubscriber",
  "version": "2.4.4",
  "icons": {
    "48": "icons/logo.svg"
  },
  "permissions": [
    "activeTab",
    "storage",
    "unlimitedStorage",
    "downloads",
    "cookies",
    "clipboardWrite",
    "*://fanfox.net/*",
    "*://*.mangatown.com/*",
    "*://*.webtoons.com/*",
    "*://mangahere.cc/*",
    "*://*.mangahere.cc/*",
    "*://manganato.com/*",
    "*://chapmanganato.to/*",
    "*://www.mangakakalot.gg/*",
    "*://www.natomanga.com/*",
    "*://www.isekaiscan.top/*",
    "*://mangadex.org/*",
    "*://api.mangadex.org/*",
    "*://*.mangago.me/*",
    "*://manhuaplus.org/*",
    "*://api.paste.ee/*"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "icons/logo.svg",
    "default_title": "MangasSub",
    "default_popup": "popup/popup.html"
  },
  "background": {
    "scripts": [
      "background_tasks/background_script.js"
    ]
  },
  "content_scripts": [
    {
      "run_at": "document_start",
      "matches": [
        "*://www.mangahere.cc/manga/*",
        "*://m.mangahere.cc/manga/*",
        "*://fanfox.net/manga/*",
        "*://m.fanfox.net/manga/*",
        "*://fanfox.net//manga/*",
        "*://m.fanfox.net//manga/*",
        "*://www.mangatown.com/manga/*",
        "*://m.mangatown.com/manga/*",
        "*://www.webtoons.com/*/*/*",
        "*://m.webtoons.com/*/*/*",
        "*://manganato.com/*",
        "*://chapmanganato.to/*/*",
        "*://www.mangakakalot.gg/*",
        "*://www.natomanga.com/*",
        "*://www.isekaiscan.top/*",
        "*://mangadex.org/*",
        "*://www.mangago.me/*",
        "*://manhuaplus.org/*"
      ],
      "js": [
        "content_tasks/content_script.js"
      ],
      "css": [
        "content_tasks/content.css"
      ]
    }
  ],
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true,
    "browser_style": true
  },
  "web_accessible_resources": [
    "icons/*.svg"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "MangasSubscriber@Lullabee",
      "strict_min_version": "120.0"
    },
    "gecko_android": {
      "strict_min_version": "120.0"
    }
  }
}