Examine source code of LifePrice

{
  "manifest_version": 2,
  "name": "LifePrice",
  "version": "1.0",
  "description": "Converts all prices to hours of your life wasted on working to afford it",
  "options_ui": {
    "page": "options.html",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "https://*.ebay.com/*",
        "https://*.amazon.com/*"
      ],
      "js": [
        "LifePrice.js"
      ]
    }
  ],
  "browser_action": {
    "default_title": "LifePrice",
    "default_popup": "options.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "lifeprice@o2.pl",
      "strict_min_version": "48.0"
    }
  }
}