IOS 12 PWA support
PWAs are a complex collection of features and functionalities. Apple added an initial support for some PWA characteristics in iOS 11.3 in march 2018. You can read a really good explanation here, with their significant limitations:
Progressive Web Apps on iOS are here https://medium.com/@firt/progressive-web-apps-on-ios-are-here-d00430dee3a7
Unfortunately iOS 12.0 doesn't seem to have improved the support in any significant way.
SEP2019 UPDATE: iOS 13.0 is here, and with it many bug fixes regarding PWAs, new installation UI and other stuff. But still no push notifications: https://medium.com/@firt/iphone-11-ipados-and-ios-13-for-pwas-and-web-development-5d5d9071cc49
MAR2019 UPDATE: This is the definitive state of PWA support in iOS 12.2 stable. It's improving but it's still a long journey: https://medium.com/@firt/whats-new-on-ios-12-2-for-progressive-web-apps-75c348f8e945
JAN2019 UPDATE: It seems like Apple is moving forward! Beta1 of iOS 12.2 has improved the PWA support. Still no push notifications though: https://medium.com/@firt/pwas-on-ios-12-2-beta-the-good-the-bad-and-the-not-sure-yet-if-good-a37b6fa6afbf https://medium.com/dev-channel/progressive-web-app-progress-in-ios-12-2-beta-1-build-16e5181f-a18cd05ca361