Add import.meta.envName for build EnvName

[maximepvrt]

Describe the feature

Describe the feature

The current implementation of envName in Nuxt allows for custom environment names (e.g., staging) to be defined at build time, as per the documentation https://nuxt.com/docs/api/commands/build#options & https://nuxt.com/docs/getting-started/configuration#environment-overrides. However, there is no straightforward way to access this custom envName at runtime.

Proposal:
Introduce import.meta.envName to reflect the custom envName defined during the build process. By default, it would to return production, development, or test, but when a custom envName is provided, it would return the defined value (e.g., staging).

Use Cases:

1. Styling and Customization:

   if (import.meta.envName === 'staging') {
       setLogoColor('blue');
   }

2. Third-Party Module Configuration:

   import * as Sentry from '@sentry/browser';
   
   Sentry.init({
       dsn: 'https://example@sentry.io/12345',
       environment: import.meta.envName, // Pass environment, 'staging' for example
   });

Additional information

• Would you be willing to help implement this feature?

[maximepvrt]

linked to nuxt/nuxt#30776