fix: preview mode by using the node canonical routes

[boazpoolman]

This pull request is for: (mark with an "x")

• [ ] examples/*
• [x] modules/next
• [ ] packages/next-drupal
• [ ] starters/basic-starter
• [ ] starters/graphql-starter
• [ ] starters/pages-starter
• [ ] Other

GitHub Issue: # #857

Describe your changes

Allow the canonical to be used for the Headless Iframe view.

I've also added a patch with the same changes. This patch can be added directly in your composer.json

canonical.patch