Examine source code of Calm New Tab

{
  "manifest_version": 2,
  "name": "Calm New Tab",
  "short_name": "Calm",
  "author": "Brendan Viscomi",
  "version": "0.1.3resigned1",
  "description": "Replace your new tab page with a relaxing photo. No frills, no tracking, open source.",
  "homepage_url": "https://github.com/brendanv/calm-new-tab",
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "permissions": [
    "storage",
    "unlimitedStorage"
  ],
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_title": "Calm New Tab",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "{ad9acb11-1016-4d4a-bc70-6b3ba7c53981}"
    }
  },
  "developer": {
    "name": "Brendan Viscomi",
    "url": "https://github.com/brendanv/calm-new-tab"
  }
}