Examine source code of Very Simple Notepad

{
  "manifest_version": 2,
  "name": "Simple Notepad",
  "description": "Simple notepad extension that saves what you jot down",
  "version": "1.0",
  "icons": {
    "19": "imgs/icon19.png",
    "48": "imgs/icon48.png",
    "128": "imgs/icon128.png"
  },
  "browser_action": {
    "default_icon": "imgs/icon19.png",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "popup.js"
    ]
  },
  "permissions": [
    "activeTab",
    "storage"
  ]
}