Recommended and mentioned products
You should not mistake PWAs with desktop or native applications built with Electron.js or Nativescript though - they do only run on the browser's context and have no access to device specific APIs.
Open source API documentation browser with instant fuzzy search, offline mode, keyboard shortcuts, and more
Take devdocs.io. The site offers its full content within a Progressive Webapp (PWA) that will even be available if your computer or mobile phone is off the net, given you have installed it when visiting the website.