Examine source code of GCal Background

{
  "manifest_version": 3,
  "name": "GCal Background",
  "version": "2.1.0",
  "description": "Personalise Google Calendar with a custom background, Apple-style events, and custom font.",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "action": {
    "default_popup": "popup/popup.html",
    "default_title": "GCal Background"
  },
  "background": {
    "scripts": [
      "background/background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://calendar.google.com/*"
      ],
      "js": [
        "content/content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "storage",
    "tabs"
  ],
  "host_permissions": [
    "*://calendar.google.com/*"
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "fonts/*.woff"
      ],
      "matches": [
        "*://calendar.google.com/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "gcal-background@extension",
      "strict_min_version": "142.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    }
  }
}