Examine source code of Inline Currency Converter

{
  "manifest_version": 2,
  "name": "Inline Currency Converter",
  "version": "1.0",
  "description": "Converts selected currency amounts to any target currency.",
  "author": "fazilus",
  "browser_specific_settings": {
    "gecko": {
      "id": "inline-currency-converter@fazilus",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "permissions": [
    "storage",
    "*://api.exchangerate-api.com/*"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_title": "Settings - Inline Currency Converter"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "currencies.js",
        "content.js"
      ],
      "css": [
        "content.css"
      ]
    }
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  }
}