Examine source code of Flexo - Flexbox helper

{
  "description": "A browser extension for testing CSS flexbox rules.",
  "manifest_version": 2,
  "name": "Flexo - Flexbox helper",
  "version": "1.0",
  "homepage_url": "https://mijokristo.com",
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "48": "icons/icon-48.png",
      "128": "icons/icon-128.png"
    }
  },
  "icons": {
    "16": "icons/icon-16.png",
    "48": "icons/icon-48.png",
    "128": "icons/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "code.js",
        "jquery.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "newtab.html"
  },
  "permissions": [
    "<all_urls>",
    "contextMenus",
    "notifications",
    "storage"
  ],
  "applications": {
    "gecko": {
      "id": "mijo@mijokristo.com"
    }
  }
}