feat: Show hint to update CLI when there's a new version available

[MariadeAnton]

What problem does this feature solve?

Saves mental energy from users, improves DX :)

When running the CLI with an older version it says:

›   Warning: checkly update available from 4.7.0 to 4.9.1.

It'd be nice if it were to have a hint to remind folks how to update it.

How would you implement this feature?

i.e.

 ›   Warning: checkly update available from 4.7.0 to 4.9.1.
 ›   use: npm install checkly@latest