Add customTabs option

[Atinux]

Example:

export default defineNuxtConfig({
  modules: ['@nuxt/devtools'],
  devtools: {
    customTabs: [
       {
           name: 'my-admin',
           title: 'My Admin',
           icon: 'carbon:apps',
           view: {
             type: 'iframe',
             src: 'http://localhost:80080/admin'
            },
       }
    ]
  }
})