feat(cli): add --delay/-d option

[nashashibi]

Adds an optional --delay (-d short) option to the CLI to delay responses.

Changes:

• added a global middleware in app.js with a setTimeout that invokes next after the specified delay duration.
• updated the executable bin logic to accept the '--delay' flag and pass it down to the createApp function.

[lucasdemoraesc]

Any chance of this being released soon? This is very important while working with server-side requests.

Thanks for the work @nashashibi

[luthfianum]

Great job! This is an important feature for testing. Thank you for handling this so well. 👍

[aadrian]

@typicode any chance merging this ?

Thank you.