PWA (Progressive Web App)
UpUp
参考：
UpUp – The Offline First Library [Official]
TalAter/UpUp: Easily create sites that work offline as well as online – GitHub
Getting Started with Offline First using UpUp Tutorial | UpUp [Official]
Web サイトを PWA (Progressive Web App) に変える簡単な手順 翻訳 | TechRacho
iOS
参考：