Examine source code of Unit Converter

{
  "manifest_version": 2,
  "name": "Unit Converter",
  "version": "1.0.1",
  "description": "Select text containing measurements and instantly see conversions in a tooltip.",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "icons": {
    "16": "icons/icon-16.png",
    "32": "icons/icon-32.png",
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_action": {
    "default_icon": {
      "16": "icons/icon-16.png",
      "32": "icons/icon-32.png",
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_popup": "popup/popup.html",
    "default_title": "Unit Converter Settings"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "converter.js",
        "content.js"
      ],
      "css": [
        "tooltip.css"
      ]
    }
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "unit-converter@moshib.in",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}