Examine source code of UAS Speed Controller

{
  "manifest_version": 2,
  "name": "UAS Speed Controller",
  "version": "1.2",
  "description": "Control video playback speed for UAS iframe players",
  "permissions": [
    "activeTab",
    "tabs",
    "https://campus.ua.school/campus/*"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    },
    "default_title": "UAS Speed Controller"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "https://campus.ua.school/campus/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "uas-speed-controller-mateusz-salach@nothing.com"
    }
  }
}