Examine source code of Youtube Start

{
  "manifest_version": 2,
  "name": "Youtube Start",
  "version": "1.0",
  "description": "A simple menu to upload and watch youtube videos and browse channels",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/beastify",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Youtube Start",
    "default_popup": "youtube start.html"
  }
}