Examine source code of GMail: search in inbox

{
  "manifest_version": 2,
  "name": "GMail: search in inbox",
  "version": "1.0.0",
  "description": "Adds a Gmail search button and Ctrl+Enter shortcut that search the current query within the inbox.",
  "icons": {
    "16": "assets/icon-16.png",
    "32": "assets/icon-32.png",
    "48": "assets/icon-48.png",
    "128": "assets/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "https://mail.google.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "gmail-search-in-inbox@example.local",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}