Add `--ci` parameter to examples

[phh]

Using --ci can save you if you accidently add a ->only() to one of your tests, which would prevent the whole testsuite from running. See Only plugin

I guess the idea behind --ci was also well. To run it during continuous integration :)

[owenvoke]

Personally, I think this makes sense. But 🤷🏻 Also, when reviewing this I was thinking it's kind of annoying to have to use --ci, so thought perhaps it could be auto-detected (I've opened a draft PR to suggest this: https://github.com/pestphp/pest/pull/1114).

[phh]

@owenvoke Thanks! I really agree with you. Setting --ci in CI by default seems like a very Laravel-y thing to do.

I personally would like it to automatically resolve that for me :D