How to create registry entries using squirrel.windows

I am creating an Electron application, and am using electron-winstaller to build the installer, which uses squirrel.windows. Inside of one of the example code snippets has this section:

const squirrelEvent = process.argv[1];
switch (squirrelEvent) {
  case '--squirrel-install':
  case '--squirrel-updated':
    // Optionally do things such as:
    // - Add your .exe to the PATH
    // - Write to the registry for things like file associations and
    // explorer context menus

    // Install desktop and start menu shortcuts
    spawnUpdate(['--createShortcut', exeName]);

    setTimeout(app.quit, 1000);
    return true;

  case '--squirrel-uninstall':
    // Undo anything you did in the --squirrel-install and
    // --squirrel-updated handlers

    // Remove desktop and start menu shortcuts
    spawnUpdate(['--removeShortcut', exeName]);

    setTimeout(app.quit, 1000);
    return true;

  case '--squirrel-obsolete':
    // This is called on the outgoing version of your app before
    // we update to the new version - it's the opposite of
    // --squirrel-updated

    app.quit();
    return true;
  }
}

In the section above that says "- Write to the registry for things like file associations and explorer context menus.". I would like to add registry entries here, but when looking at the squirrel documentation I could not figure how to do this. I could not find any examples online. Anyone have any ideas?