yarn add -D nuxt-png-to-ico # or npm install --save-dev nuxt-png-to-ico

// prepare input and output path
const inputIconFilePath = resolve(__dirname, './static/icon.png')
const outputIconFilePath = resolve(__dirname, './static/favicon.ico')

{
  buildModules: [
    [
      'nuxt-png-to-ico',
      {
        /* module options */

        inputIconFilePath,
        outputIconFilePath
      }
    ]
  ]
}