Examine source code of Break Reminder

{
  "manifest_version": 2,
  "name": "Daily Website Timer",
  "version": "2.1",
  "description": "Displays the time spent on the current website today. Resets daily.",
  "permissions": [
    "tabs",
    "storage",
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Website Timer Settings"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{4eb61353-6042-4e1a-9a0a-e5a35b7548d8}"
    }
  }
}