Use .env "NUXT_SITE_URL" for "NUXT_PUBLIC_I18N_BASE_URL"

[MickL]

Describe the feature

@nuxtjs/seo is using NUXT_SITE_URL as env variable while @nuxtjs/i18n is using NUXT_PUBLIC_I18N_BASE_URL. This leads to having two environment variables with the same content.

I would suggest for @nuxtjs/i18n to use NUXT_SITE_URL as well, but overwrite with NUXT_PUBLIC_I18N_BASE_URL if set.

Possibly related: #2474

Additional information

• Would you be willing to help implement this feature?
• Could this feature be implemented as a module?

Final checks

• Read the contribution guide (The contribution guideline of nuxt-modules/i18n is compliant with Nuxt too).
• Check existing discussions and issues.