Examine source code of Switch to localhost

{
  "description": "Switch to localhost URL",
  "manifest_version": 2,
  "name": "Switch to localhost",
  "version": "1.1",
  "homepage_url": "https://github.com/guillaumebriday/switch-to-localhost",
  "icons": {
    "128": "icons/icon.png"
  },
  "browser_action": {
    "default_title": "Switch to localhost",
    "default_icon": "icons/icon.png"
  },
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options.html"
  }
}