Examine source code of uflix-next-button

{
  "manifest_version": 2,
  "name": "uflix-next-button",
  "version": "2.0",
  "description": "Adds a next button to uflix series",
  "icons": {
    "48": "icons/slw-icon-48.png",
    "96": "icons/slw-icon-96.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://uflix.cc/episode/*"
      ],
      "js": [
        "uflix-next-button.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "uflix-next-button@skadlitwiniwracaja.ddns.net"
    }
  }
}