Yes, Ionic can be used to develop a progressive web app (PWA), you don’t need to create iOS or Android builds if you don’t want to. The app can be locally served during development with
ionic serve and built for production with
ionic build --prod. Then you just need to upload the
www directory to your web server or service like Firebase, GitHub Pages, Netlify, etc.
I recommend Ionic 4, as it uses the Angular Router and it’s more URL/SEO friendly. If you’re also targeting desktop devices, check out the article I wrote on the Official Ionic Blog: https://blog.ionicframework.com/tips-tricks-for-ionic-on-desktop/. Mike Hartington from the Ionic team also recorded a great screencast about How to build a Progressive Web App (PWA).