Examine source code of Timeless

{
  "manifest_version": 2,
  "name": "Timeless",
  "version": "1.1.0",
  "description": "Hides time and progress bar on Twitch and YouTube",
  "icons": {
    "48": "icons/menu.svg",
    "96": "icons/menu.svg"
  },
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_icon": "icons/menu.svg",
    "default_title": "Timeless",
    "default_popup": "menu.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*",
        "*://*.twitch.tv/*"
      ],
      "js": [
        "js/main.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{abbcbde2-2c6c-4b39-bab0-d1a8d3abcc93}"
    }
  }
}