Multilingual support

[Decipher]

Is your feature request related to a problem? Please describe.
As a user I want multilingual support for the decoupled demo.

Describe the solution you'd like

• Ensure the Decoupled Router supports langcodes: https://www.drupal.org/project/decoupled_router/issues/3111456#comment-14093342

Describe alternatives you've considered
N/A

Additional context
druxt/druxt.js#158