Examine source code of Metrication

{
  "manifest_version": 2,
  "name": "Metrication",
  "version": "0.0.7",
  "default_locale": "en",
  "author": "DeltaMikeCharlie",
  "homepage_url": "http://deltamikecharlie.yolasite.com/metrication.php",
  "browser_specific_settings": {
    "gecko": {
      "id": "metrication@deltamikecharlie",
      "strict_min_version": "54.0"
    }
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "permissions": [
    "<all_urls>",
    "clipboardWrite",
    "tabs",
    "menus",
    "storage"
  ],
  "description": "__MSG_extensionDescription__",
  "icons": {
    "16": "icons/icon.svg",
    "48": "icons/icon.svg",
    "60": "icons/icon.svg",
    "96": "icons/icon.svg",
    "128": "icons/icon.svg"
  },
  "web_accessible_resources": [
    "icons/icon40.png",
    "icons/clipboard.png",
    "metrication.css"
  ],
  "page_action": {
    "show_matches": [
      "<all_urls>"
    ],
    "browser_style": true,
    "default_icon": {
      "19": "icons/icon.svg",
      "38": "icons/icon.svg"
    },
    "default_title": "__MSG_menuItemMain__"
  },
  "background": {
    "scripts": [
      "conversions.js",
      "background.js"
    ],
    "persistent": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "metrication.js"
      ],
      "css": [
        "metrication.css"
      ]
    }
  ]
}