Examine source code of Youtube dark mode 2

{
  "name": "Youtube dark mode 2",
  "short_name": "Youtube black theme",
  "manifest_version": 2,
  "version": "2.5.1.1",
  "description": "YouTube dark mode 2 reduces eyes strain and saves battery.",
  "browser_action": {
    "default_icon": "48.png",
    "default_title": "Toggle YouTube mode"
  },
  "background": {
    "scripts": [
      "bgr.js"
    ],
    "persistent": false
  },
  "permissions": [
    "tabs",
    "activeTab",
    "storage",
    "<all_urls>"
  ],
  "icons": {
    "16": "16.png",
    "48": "48.png",
    "128": "128.png"
  }
}