Examine source code of Gmail Attachment Compressor

{
  "manifest_version": 2,
  "name": "Gmail Attachment Compressor",
  "version": "2.0",
  "description": "Adds an Attach Compressed button in Gmail that zips selected files before uploading.",
  "icons": {
    "16": "icons/icon16.png",
    "32": "icons/icon32.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "browser_action": {
    "default_title": "Gmail Attachment Compressor",
    "default_icon": {
      "16": "icons/icon16.png",
      "32": "icons/icon32.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "options_ui": {
    "page": "options/options.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": [
    "storage",
    "https://mail.google.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "gmail-attachment-compressor@example.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      },
      "strict_min_version": "113.0"
    }
  }
}