[BUG] Implement Quit Public post privacy like the Android app

[todoneunl]

Is there an existing issue for this?

• I have searched the issues (both open and closed)

Current Behavior

The Android app now seems to have Quit Public AKA Unlisted as a post privacy option. This is a good decision, because when people have set their post privacy to Quit Public in the web-app as default, it gives confusion in the iOS app.

So please implement that here as well, so the confusion will be resolved for iOS app users as well.