Fix wrong yarn installation cli commands #22435
Description
Existing documentation URL(s)
https://developers.cloudflare.com/workers/frameworks/framework-guides/nextjs/
In some sections the documentation says "yarn install @opennextjs/cloudflare@latest". This will throw an error since its not an valid cli command with yarn.
What changes are you suggesting?
Replace 'install' with 'add' to use the proper yarn syntax
Additional information
No response