examples: improve DX while copying command to create new project

[JamBalaya56562]

Description

Follow up #38410.
Some examples remain the multiple commands in a single block, and we couldn't use copy button to select one line.
With this change users would be able to copy the command (using their choice package manager) with a single click using the github copy feature.

CC: @samcx

Adding or Updating Examples

• The "examples guidelines" are followed from our contributing doc https://github.com/vercel/next.js/blob/canary/contributing/examples/adding-examples.md
• Make sure the linting passes by running pnpm build && pnpm lint. See https://github.com/vercel/next.js/blob/canary/contributing/repository/linting.md

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 7423a2b

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[ijjk]

Allow CI Workflow Run

• approve CI run for commit: 4d7e22d

Note: this should only be enabled once the PR is ready to go and can only be enabled by a maintainer

[samcx]

Thank you for submitting a PR!