Examine source code of floatingcube

{
  "manifest_version": 2,
  "name": "floatingcube",
  "version": "1.0",
  "description": "Noting, finding, easy access to sugarcube variables for sugarcube pages.",
  "browser_specific_settings": {
    "gecko": {
      "id": "sleepingkirby@gmail.com-floatingcube",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "activeTab",
    "tabs",
    "scripting",
    "storage"
  ],
  "icons": {
    "64": "icons/logo64.png",
    "96": "icons/logo96.png",
    "128": "icons/logo128.png"
  },
  "browser_action": {
    "default_icon": {
      "64": "icons/logo64.png",
      "96": "icons/logo96.png",
      "128": "icons/logo128.png"
    },
    "default_title": "floating cube",
    "default_popup": "popup/menu.html"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "./content_scripts/main.js"
      ],
      "all_frames": true,
      "run_at": "document_idle"
    }
  ]
}