Examine source code of URLCheck

{
  "manifest_version": 2,
  "name": "URLCheck",
  "description": "Shows the real destination of the current page in large, high-contrast text.",
  "version": "0.2.2",
  "icons": {
    "16": "icon/16.png",
    "32": "icon/32.png",
    "48": "icon/48.png",
    "96": "icon/96.png",
    "128": "icon/128.png"
  },
  "permissions": [
    "webNavigation",
    "webRequest",
    "tabs",
    "scripting",
    "storage",
    "alarms"
  ],
  "optional_permissions": [
    "<all_urls>"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "urlcheck@urlcheck.app",
      "strict_min_version": "115.0",
      "data_collection_permissions": {
        "required": [
          "authenticationInfo"
        ]
      }
    }
  },
  "web_accessible_resources": [
    "fonts/*",
    "entitlement-jwks.json"
  ],
  "commands": {
    "summon-bubble": {
      "suggested_key": {
        "default": "Ctrl+Shift+U",
        "mac": "Command+Shift+U"
      },
      "description": "Summon the URLCheck on the current tab"
    }
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "URLCheck",
    "default_popup": "popup.html"
  },
  "options_ui": {
    "open_in_tab": true,
    "page": "options.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "run_at": "document_idle",
      "js": [
        "content-scripts/content.js"
      ]
    }
  ]
}