feat(strategy): add PREFIX_AND_DEFAULT strategy

[odanado]

This strategy generates the following routing.

nuxt.config.js:

{
  strategy: 'prefix_and_default',
  locales: [
    {
      code: 'ja',
      iso: 'ja',
      name: '日本語',
    },
    {
      code: 'en',
      iso: 'en-US',
      name: 'English',
    },
  ],
  defaultLocale: 'en',
}

routing:

[
  {
    path: "/",
    component: _3237362a,
    name: "index___en"
  },
  {
    path: "/en",
    component: _3237362a,
    name: "index___en"
  },
  {
    path: "/ja",
    component: _3237362a,
    name: "index___ja"
  },
]

demo: https://relaxed-snyder-764840.netlify.com/

[paulgv]

Thanks @odanado !