Examine source code of FollowDex

{
  "manifest_version": 2,
  "name": "FollowDex",
  "version": "1.0",
  "author": "Xéfir Destiny",
  "homepage_url": "https://mangadex.org",
  "description": "Color in red your followed mangas on MangaDex",
  "permissions": [
    "*://*.mangadex.org/*"
  ],
  "icons": {
    "48": "mangadex.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.mangadex.org/*"
      ],
      "js": [
        "followdex.js"
      ]
    }
  ]
}