Examine source code of That Cool Page

{
  "manifest_version": 2,
  "name": "That Cool Page",
  "version": "1.0",
  "description": "Recommend to friend that cool page.",
  "homepage_url": "https://www.thatcoolpage.com/",
  "icons": {
    "48": "icons/forward.png"
  },
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/forward.png",
    "default_title": "That Cool Page"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  }
}