Fixes draft preview links when i18n is enabled in Next.js config

[apmatthews]

Description

Next.js includes support for internationalized routing through the i18n config. The i18n config affects redirects in such a way that our existing preview regex doesn't match on any root path (i.e. /, /en, /fr, etc.). This PR adds an extra redirect rule to handle the special cases that i18n introduces.

Preview links that target a root path are typically draft posts that have not been published. These posts don't have a post slug yet, so they are identified only by query params on the site's root path.

Testing

Using the following config...

const { withFaust } = require('@faustjs/next');

/**
 * @type {import('next').NextConfig}
 **/
module.exports = withFaust({
  i18n: {
    locales: ['en', 'fr'],
    defaultLocale: 'en',
  },
});

you should see these results:

Before

Status	Preview URL	Result
Draft	/?preview=true&p=1&typeName=Post	/?preview=true&p=1&typeName=Post	🔴
Draft	/en?preview=true&p=1&typeName=Post	/?preview=true&p=1&typeName=Post	🔴
Draft	/fr?preview=true&p=1&typeName=Post	/fr?preview=true&p=1&typeName=Post	🔴
Published	/posts/hello-world?preview=true&p=1&typeName=Post	/preview?preview=true&p=1&typeName=Post	🟢
Published	/fr/posts/hello-world?preview=true&p=1&typeName=Post	/fr/preview?preview=true&p=1&typeName=Post	🟢

After

Status	Preview URL	Result
Draft	/?preview=true&p=1&typeName=Post	/preview?preview=true&p=1&typeName=Post	🟢
Draft	/en?preview=true&p=1&typeName=Post	/preview?preview=true&p=1&typeName=Post	🟢
Draft	/fr?preview=true&p=1&typeName=Post	/fr/preview?preview=true&p=1&typeName=Post	🟢
Published	/posts/hello-world?preview=true&p=1&typeName=Post	/preview?preview=true&p=1&typeName=Post	🟢
Published	/fr/posts/hello-world?preview=true&p=1&typeName=Post	/fr/preview?preview=true&p=1&typeName=Post	🟢

[changeset-bot]

🦋 Changeset detected

Latest commit: 4ddc114

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@faustjs/next	Patch

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[theodesp]

LGTM