Add is_review variable

[edalzell]

Add is_review variable to the entry so you can change the behaviour if you're viewing an entry in "review" mode.

References https://github.com/transformstudios/zakat-v3/issues/1993
References https://github.com/transformstudios/zakat-v3/issues/1996

[marcorieser]

@edalzell nice one! only thing i'm wondering is: is simulating live_preview the right way to do it? for us, sure! but is it what folks expect when they open a page in review mode? for example, folks might add some js stuff when being in the live preview mode (https://jacksleight.dev/posts/hot-reloading-statamic-s-live-preview-in-a-traditonal-mpa). couldnt we do ->setSupplement('is_review', true) and check for that in antlers like {{ if live_preview || is_review }} , if to use the tw cdn?

[edalzell]

ya good point, I use to have something like that in Review, I'll bring it back.